Cardiac electrical lead

ABSTRACT

A bipolar cardiac lead ( 100 ) is provided and includes a connector pin ( 112 ), a connector insulator ( 116 ), and a ring connector ( 130 ). The connector pin ( 112 ) has a proximal end and a distal end, and the proximal end is configured to engage an electrical stimulation device. The connector insulator ( 116 ) is coupled to the distal end of the connector pin ( 112 ) and may define a bore ( 118 ) configured for receiving a portion of the connector pin ( 112 ). The connector insulator ( 116 ) provides electrical insulation between the connector pin ( 112 ) and the ring connector ( 130 ). The ring connector ( 130 ) is coupled to the connector insulator ( 116 ) with a snap-fit connection and may be disposed around a portion of the connector insulator ( 116 ). The bipolar cardiac lead ( 100 ) may be an active or a passive lead.

TECHNICAL FIELD

The present disclosure relates generally to implantable electricalleads. More particularly, the present disclosure relates to connectionend features of implantable electrical leads where the lead is connectedto an associated defibrillator, pacemaker, or other electricalstimulation device.

BACKGROUND

Electrodes are often used to stimulate contraction of the heart. Forexample, when a patient's heart is functioning with an abnormal rhythm,electrical energy may be applied to the heart via the electrodes toreturn the heart to a normal rhythm. In some cases this procedure may bean isolated event while in other cases a more frequent, regular, or evencontinuous process is used. In these cases electrodes may beincorporated into a lead that is used with a pacemaker, defibrillator,or other electrical stimulation device such that pacing pulses may bedelivered, for example, to an atrium or ventricle of a heart. The systemincluding the electrical stimulation device and the lead may beimplantable and, thus, used over long periods of time.

In general, a lead includes a pair of electrodes disposed at a distalend of the lead which may be positioned generally in the right ventricleor the right atrium of the heart. The proximal end of the lead may becoupled to a defibrillator or a pacemaker and conductors may deliverelectrical impulses along the length of the lead to the electrodethereby delivering pacing pulses to the heart.

There are at least two conventional types of leads. The first type oflead is referred to as an active electrical lead with an activemechanism at the distal end. The second type of lead is referred to as apassive electrical lead with a passive mechanism at the distal end.

The distal end of a typical active electrical lead may include a helicalanchor electrode designed to be actuated and axially extend and/orrotate out of a tip portion of the lead to engage or embed into theendocardium. The distal end of a typical passive electrical lead mayinclude an anchor type fixation mechanism designed to anchor the distalend in the heart. The fixation mechanism for a passive lead, forexample, may include one or more radially spaced tines that secure thedistal end in the heart.

The proximal end of pacemaker and defibrillator leads are commonlydesigned and manufactured to a standard such as China Standard YY/T0491-2004//ISO 5841-3, 2000. The standard is applicable to both activeand passive pacemaker or defibrillator leads. Within that standard,medical device implant companies commonly have their own unique designs.Among the technologies used to meet the standard, are laser welding andmetal crimping resulting in highly reliable pacemaker and defibrillatorlead joint connections.

The design of defibrillator and pacemaker leads has evolved over time.Over time and at present, the proximal end of an active electrical leadand the proximal end of a passive electrical lead are generally designeddifferently due to their functional differences. That is, the proximalend of an active lead may be designed to actuate and/or control thedistal active mechanism, while the proximal end of a passive lead maynot include such actuation and/or control features. System designs andassembly processes of the passive and active electrical leads are, thus,different. As a result, the overall cost of having significant differentsystem designs and assembly processes is relatively high and a systemhaving common features or similar or exchangeable components between anactive electrical lead and a passive electrical lead may be lessexpensive and more attractive to consumers.

The information included in this Background section of thespecification, including any references cited herein and any descriptionor discussion thereof, is included for technical reference purposes onlyand is not to be regarded subject matter by which the scope of theinvention as defined in the claims is to be bound.

SUMMARY

In one implementation, a bipolar cardiac lead is provided. The leadincludes a connector pin, a connector insulator, and a ring connector.The connector pin has a proximal end and a distal end, and the proximalend is configured to engage an electrical stimulation device. Theconnector insulator is coupled to the distal end of the connector pinand may define a bore configured to receive a portion of the connectorpin. The connector insulator provides electrical insulation between theconnector pin and the ring connector. The ring connector is coupled tothe connector insulator with a snap-fit connection and may be disposedaround a portion of the connector insulator. The bipolar cardiac leadmay be an active or a passive lead.

In another implementation, a connector insulator is provided. Theconnector insulator includes a body, a proximal extension extending fromthe body in a proximal direction, and a distal extension extending fromthe body in a distal direction. The proximal extension is connectable toa connector pin, and the distal extension is connectable to a ringconnector. The distal extension includes at least one tab extendingradially outward from an outer surface of the distal extension. The atleast one tab is spaced from the body in a distal direction to define anannular recess between the at least one tab and the body.

In another implementation, a ring connector is provided. The ringconnector includes a band portion and a crimp portion arranged distallyto the band portion. The band portion includes an exposed outer surfaceand an inner wall. The exposed outer surface is configured toelectrically communicate with an electrical stimulation device, and theinner wall defines an inner cavity configured to receive a portion of aconnector insulator. The inner wall includes an annular groove spaceddistally from a proximal face of the ring connector to define a radiallyinturned lip intermediate the proximal face and the annular groove. Thering connector may include a slot portion arranged intermediate the bandportion and the crimp portion.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. A moreextensive presentation of features, details, utilities, and advantagesof the present invention is provided in the following writtendescription of various embodiments of the invention, illustrated in theaccompanying drawings, and defined in the appended claims.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an isometric view of an exemplary embodiment of an implantablemedical electrical lead with an active electrode.

FIG. 2 is a cross-sectional view of a proximal end of the lead of FIG.1.

FIG. 3 is an isometric view of a connector pin of the lead of FIGS. 1and 2.

FIG. 4 is an isometric view of a pin sleeve of the lead of FIGS. 1 and2.

FIGS. 5A and 5B are an isometric view and an isometric cross-sectionalview, respectively, of a connector insulator of the lead of FIGS. 1 and2.

FIGS. 6A and 6B are an isometric view and an isometric cross-sectionalview, respectively, of a proximal seal of the lead of FIGS. 1 and 2.

FIGS. 7A and 7B are an isometric view and an isometric cross-sectionalview, respectively, of a ring connector of the lead of FIGS. 1 and 2.

FIGS. 7C and 7D are an isometric view and an isometric cross-sectionalview, respectively, of an alternative ring connector.

FIGS. 8A and 8B are an isometric view and an isometric cross-sectionalview, respectively, of a ring sleeve of the lead of FIGS. 1 and 2.

FIGS. 9A and 9B are an isometric view and an isometric cross-sectionalview, respectively, of a boot seal of the lead of FIGS. 1 and 2.

FIGS. 10A and 10B are an isometric view and an isometric cross-sectionalview, respectively, of a distal end of the lead of FIG. 1 with an activeelectrode tip configuration.

FIG. 10C is an isometric cross-sectional view of the active electrodetip configuration of FIG. 10B with the helical anchor electrode in anextended position.

FIG. 11 is an isometric view of a tip electrode pin of the activeelectrode of FIGS. 10A and 10B.

FIG. 12 is an isometric view of a helical anchor electrode of the activeelectrode tip of FIGS. 10A and 10B.

FIG. 13 is an isometric view of helical anchor electrode, astopper/spacer ring, and a seal ring attached to the tip electrode pinof the active electrode tip of FIGS. 10A and 10B.

FIGS. 14A and 14B are an isometric view and an isometric cross-sectionalview, respectively, of an intermediate connector mount of the activeelectrode tip of FIGS. 10A and 10B.

FIGS. 15A and 15B are an isometric view and an isometric cross-sectionalview, respectively, of a ring electrode of the active electrode tip ofFIGS. 10A and 10B.

FIG. 16 is an isometric view of a spacer/stopper ring of the activeelectrode tip of FIGS. 10A and 10B.

FIGS. 17A and 17B are an isometric view and an isometric cross-sectionalview, respectively, of a distal seal ring of the active electrode tip ofFIGS. 10A and 10B.

FIGS. 18A and 18B are an isometric view and an isometric cross-sectionalview, respectively, of a tip housing of the active electrode tip ofFIGS. 10A and 10B.

FIG. 19 is a view showing an exemplary embodiment of a marker bandformed of a radiopaque material.

FIGS. 20A and 20B are a distal isometric view and a proximal isometricview, respectively, of a soft tip plug of the active electrode tip ofFIGS. 10A and 10B.

FIG. 21 is a cross-sectional view of an alternative proximal end of thelead of FIG. 1 with a snap-fit connection between the connectorinsulator and the ring connector.

FIGS. 22A, 22B, and 22C are an isometric view, an isometriccross-sectional view, and a distal, elevation side view, respectively,of a connector insulator of the lead of FIGS. 1 and 21.

FIGS. 22D, 22E, and 22F are an isometric view, an isometriccross-sectional view, and a distal, elevation side view, respectively,of an alternative connector insulator.

FIGS. 22G, 22H, and 22I are an isometric view, an isometriccross-sectional view, and a distal, elevation side view, respectively,of another alternative connector insulator.

FIGS. 23A and 23B are an isometric view and an isometric cross-sectionalview, respectively, of a ring connector of the lead of FIGS. 1 and 21.

FIG. 24 is an isometric view of an exemplary embodiment of animplantable medical electrical lead with a passive electrode.

FIG. 25 is a cross-sectional view of a proximal end of the lead of FIG.24.

FIGS. 26A and 26B are an isometric view and an isometric cross-sectionalview, respectively, of a connector insulator of the lead of FIGS. 24 and25.

FIGS. 27A and 27B are an isometric view and an isometric cross-sectionalview, respectively, of a proximal seal of the lead of FIGS. 24 and 25.

FIGS. 28A and 28B are an isometric view and an isometric cross-sectionalview, respectively, of a distal end of the lead of FIG. 24.

FIGS. 29A and 29B are an isometric view and an isometric cross-sectionalview, respectively, of a tip electrode of the lead of FIGS. 24, 28A, and28B.

FIGS. 30A and 30B are an isometric view and an isometric cross-sectionalview, respectively, of a passive tip sheath of the lead of FIGS. 24,28A, and 28B.

FIGS. 30C and 30D are an isometric view and an isometric cross-sectionalview, respectively, of an alternative passive tip sheath.

FIG. 31 is an isometric view of a steroid insert for the passive tipsheath of the lead of FIGS. 24, 28A, and 28B.

FIGS. 32A and 32B are an isometric view and an isometric cross-sectionalview, respectively, of a tip sleeve of the lead of FIGS. 24, 28A, and28B.

FIGS. 33A and 33B are an isometric view and an isometric cross-sectionalview, respectively, of a ring electrode of the lead of FIGS. 24, 28A,and 28B.

FIGS. 34A and 34B are an isometric view and an isometric cross-sectionalview, respectively, of an alternative ring electrode.

FIG. 35 is a cross-sectional view of an alternative proximal end of thelead of FIG. 24 with a snap-fit connection between the connectorinsulator and the ring connector.

FIGS. 36A, 36B, and 36C are an isometric view, an isometriccross-sectional view, and a distal, elevation side view, respectively,of a connector insulator of the lead of FIGS. 24 and 35.

FIGS. 36D, 36E, and 36F are an isometric view, an isometriccross-sectional view, and a distal, elevation side view, respectively,of an alternative connector insulator.

DETAILED DESCRIPTION

The present disclosure relates to an implantable electrical lead havingan active mechanism on a distal end (i.e., an active lead) or a passivemechanism on a distal end (i.e., a passive lead). The active and passiveleads may include a system of parts on a proximal end thereof that isprimarily adapted to connect to and electrically communicate with adefibrillator, pace maker, or other electrical stimulation device. It isnoted that some of the parts may be adapted to insulate between otherparts and/or between the proximal end and the electrical stimulationdevice. Additionally, for the active lead, a portion of the parts may beparticularly adapted to allow actuation and control of the activemechanism on the distal end of the lead. The system of parts may bedesigned so that many of the parts of the proximal end of the active andpassive leads are the same, thereby reducing the cost of tooling,manufacturing, and assembling the different type of leads.

FIG. 1 is an isometric view of one embodiment of an implantable medicalelectrical lead 100. The lead 100 has a proximal end 102 and a distalend 104. As shown, an active tip portion 106 may be disposed at thedistal end 104 of the lead 100 and may include a helical anchorelectrode 108. The helical anchor electrode 108 may be designed toaxially extend out of the active tip portion 106 to engage a treatmentsite of a patient such as the endocardium of a heart, for example. Thehelical anchor electrode 108 may be retractably extended distally out ofthe active tip portion 106. In operation, a conductive connector pin atthe proximal end 102 of the lead 100 may be rotated to drive a mechanismin the active tip portion 106, thereby extending the helical anchorelectrode 108 out of the tip portion 106. The rotating extension of thehelical anchor electrode 108 from the active tip portion 106 may engage(i.e., screw into) a treatment site of a patient.

Referring now to FIG. 2, the proximal end 102 of the lead 100 includes asystem of parts or pieces. The system of parts or pieces may be dividedinto three categories including inner parts relating to an innerconductor, outer parts relating to an outer conductor, and insulatingparts for electrically separating the inner parts from the outer parts.The inner parts may include a conductive connector pin 112, an innerconductor or coil 120, and a pin sleeve 122. The outer parts may includea ring connector 130, an outer conductor or coil 134, and a ring sleeve136. The inner and outer parts may be substantially separated by theinsulating parts including a connector insulator 116 and an insulatortubing 124. A proximal seal 114 and a boot seal 140 may also beprovided.

Beginning with the inner parts, the connector pin 112 may be configuredfor electrical engagement with a defibrillator, pacemaker or otherelectrical stimulation device and for communicating electrical impulsesto the inner conductor or coil 120. As such, the connector pin 112 maybe adapted at one end for plugging into a socket of an electricalstimulation device and may be adapted at another end for connecting tothe inner conductor or coil 120.

A close-up view of a connector pin 112 is shown in FIG. 3. As shown, theconnector pin 112 may include a socket end 160 and a conductor end 162and may further include a bar portion 164 extending therebetween. Thesocket end 160 of the pin 112 may be generally elongate andcylindrically-shaped and may have a diameter adapted for placement in acorrespondingly shaped socket of an electrical stimulation device. Theproximal end of the socket end 160 may include a chamfered edge 166 forguiding the pin 112 into the socket when placing the pin 112 into theelectrical device. The distal end of the socket end 160 may include asubstantially sharp or square edge 168 for abutting the connectorinsulator 116 or the proximal seal 114 as the case may be.

Exposed portions of the proximal end 102 of the lead 100, like thesocket end 160 just described, that may contact or otherwise physicallyinteract with an electrical stimulation device, may be designed to meetindustry standard specifications such as the IS-1 specification, forexample. As such, while particular parts of the proximal end 102 aredescribed herein as varying in size, diameter, length, or otherdimensional variations, in some embodiments, the exposed portions of theparts may be selected to meet such specifications or standards. However,nothing in the present disclosure should be construed to limit the partsto industry standard dimensions.

The bar portion 164 of the connector pin 112 may also be generallyelongate and cylindrically shaped and may have a diameter smaller thanthat of the socket end 160. The bar portion 164 may have a lengthselected to longitudinally secure the pin 112 relative to the connectorinsulator 116 and the proximal seal 114. That is, the length of the barportion 164 may correspond to a bore length in the connector insulator116 as shown in FIG. 2, such that longitudinal motion is substantiallyprevented relative to the connector insulator 116. As shown in FIG. 2,the socket end 160 and the bar portion 164 may include a longitudinallyextending bore 170 extending from the socket end 160 of the pin 112 tothe distal end of the bar portion 164 and exiting into a crimp zone 172within the conductor end 162 of the pin 112. This bore 170 may be sizedand adapted to receive a stylet, for example, when installing orpositioning the lead 100, or when access to the distal end 104 of thelead 100 is desired.

The conductor end 162 of the pin 112 may be substantiallycylindrically-shaped with an outer diameter slightly larger than that ofthe bar portion 164 and slightly smaller than that of the socket end160. Other relationships of diameters of the several portions of theconnector pin 112 may also be provided. For example, the conductor end162 may have an outer diameter larger than the socket end 160. In theexemplary embodiment shown in FIG. 3, the conductor end 162 may bearranged in a relatively congested area where the ring connector 130,the insulator tubing 124, the connector insulator 116, the conductor end162, the inner conductor 120, and the pin sleeve 122 all overlap. Wherethe proximal end 102 is designed to meet the IS-1 specification, forexample, restrictions on the overall outer diameter together with thecongestion may cause the outer diameter of the conductor end 162 to besmaller than the socket end 160.

The conductor end 162 of the pin 112 may include an inner cavity orcrimp zone 172 having a substantially cylindrical cross-section with adiameter defining an inner diameter of the conductor end 162 as shown inFIG. 2. The conductor end 162 may have a length selected to match orexceed the length of the pin sleeve 122, to be described below, so as toprovide suitable length for crimping the conductor 120. Other conductorend lengths may be selected and a suitable length of the cavity 172 maybe selected to ensure sufficient crimp length of the coil 120 within thecavity 172.

The conductor end 162 may include a hole or a pair of holes 174 forinspecting the crimped conductor 120 within the cavity 172. The holes174 may extend through the conductor end 162 from an outer surface andinto the cavity 172 and may be positioned near a proximal end of thecavity 172. As such, when the conductor 120 is crimped in the cavity172, a portion of the conductor 120 may be visible through the hole orholes 174 and the depth into the cavity 172 of the crimp connection maybe ascertainable to assure sufficient crimp length.

The connector pin 112 can be made from one or more of severalbiocompatible conductor materials such as stainless steel 316L or ametal alloy, MP35N, for example. The pin material may be selected to bebiocompatible and suitably conduct and transmit electrical signals froman electrical stimulation device. The material, together with the sizesof the pin 112 and the pin sleeve 122 (e.g., relative diameters and wallthicknesses), may be selected to suitably crimp the inner conductor orcoil 120 therebetween such that a reliable crimp connection is providedthat is both mechanically secure and through which electricaltransmissions can be made. It is noted that the connector pin 112 may beengineered to have sufficient strength to withstand compression forcesassociated with assembly. For example, as can be appreciated from FIG.2, the conductor end 162 of the pin 112 may be forced through the bore118 of the connector insulator 116 into the bore 119 and the bar portion164 of the pin 112 may be suitably strong to withstand such acompression force without buckling or weakening. In an effort to moresmoothly insert the pin 112, the distal end of the conductor end 162 mayinclude an exterior taper 176 as shown in FIG. 3.

An isolated view of the pin sleeve 122 is shown in FIG. 4. The pinsleeve 122 may be adapted for insertion a selected distance into theproximal end of the conductor or coil 120. As such, the pin sleeve 122may include a sleeve portion 178 and a flare portion 180. The sleeveportion 178 may be substantially cylindrically shaped for insertion intothe proximal end of the coil 120. The diameter of the sleeve portion 178may be slightly larger than that of the coil 120 to create someconnecting friction between the sleeve 122 and the coil 120 when thecoil is sleeved over the sleeve portion 178. The diameter of the pinsleeve 122 may also be selected to suitably pinch or press the coil 120against the inner surface of the cavity 172 of the conductor end 162 ofthe pin 112 when crimping the coil 120.

The sleeve portion 178 may have a length selected to sufficiently engagethe coil 120 and hold the coil 120 when the coil 120 is crimped betweenthe sleeve 178 and the inner surface of the conductor end 162 of the pin112. The flare portion 180 of the sleeve 122 may be positioned on aproximal end of the sleeve 122 and may be configured to limit or stopthe insertion distance of the sleeve 122 in the coil 120 and to preventthe sleeve 122 from passing too far into the coil 120 when crimping thecoil 120. As such, the flared portion 180 may define a graduallyincreasing diameter beginning with the diameter of the sleeve portion178 and extending to a diameter approximating the inner diameter of thecrush cavity 172 of the conductor end 162 of the pin 112. It is notedthat the proximal end of the pin sleeve 122 is shown as a flared portionin contrast to the more square or flange-like proximal end on the ringsleeve 136 of FIGS. 8A and 8B. The shape of the proximal ends of the pinsleeve 122 and ring sleeve 136 may be selected based on whether therespective part is formed from tubing or bar stock. For example, if thepart is formed from tubing, the proximal end may be flared like the pinsleeve 122 shown. However, if the part is formed from bar stock, theproximal end may be machined to be flanged like the ring sleeve 136.Other fabrication techniques and approaches may also be used.

The inner diameter of the conductor end 162 of the pin 112 and the outerdiameter of the sleeve portion 178 of the pin sleeve 122 may be selectedto suitably crimp the inner conductor or coil 120 therebetween. Forexample, the pin sleeve 122 may have an outer diameter and the wire usedfor the inner coil 120 may have a thickness. The inner diameter of thecavity 172 may be selected to be slightly less than the outer diameterof the pin sleeve 122 plus twice the wire thickness. As such, when thepin sleeve 122 is inserted into the coil 120 and the pin sleeve 122 andconductor 120 are pressed into the cavity 172 of the conductor end 162of the pin 112, the coil 120 may be crimped between the pin sleeve 122and the inner surface of the cavity 172 of the conductor end 162 of thepin 112. Consideration may be given to the thicknesses and elasticity ofthe conductor end 162 of the pin 112 and the pin sleeve 122 whenselecting suitable relative diameters.

The inner conductor or coil 120 may be an electrically conductive memberextending longitudinally along the lead 100. The conductor 120 may be inthe shape of a coil or a tubular sleeve shape may be provided. The coilshape may provide flexibility to the lead and allow for maneuverabilitywhen placing the lead, for example. The inner conductor 120 may define alongitudinally extending bore along its length for receiving a stylet orother device.

As mentioned, the inner parts may be electrically isolated from theouter parts by a system of insulating parts. A close-up view of theconnector insulator 116 is shown in FIGS. 5A and 5B. The connectorinsulator 116 may be configured for sleevably isolating the connectorpin 112 and a portion of the inner conductor 120 from the outer parts.In addition, the connector insulator 116 may be configured forsupporting a portion of the proximal seal 114. The connector insulator116 may be configured to separate the connector pin 112 from theproximal seal 114 such that the connector pin 112 may be easily rotated,thereby rotating the inner conductor or coil 120 and controlling a tipelectrode pin 105 and the helical anchor electrode 108 attached theretoon a distal end 104 of the lead 100 as shown in FIG. 10B. The connectorinsulator 116 may include a central body 182, a proximal extension 184,and a distal extension 186. The central body 182 may include asubstantially cylindrically-shaped body having an outer diameter. Thedistal extension 186 may also be substantially cylindrically-shaped andmay include an outer diameter smaller than that of the central body 182.

The distal extension 186 may extend from the central body 182 in thedistal direction from a set of cascading shoulders 188, 190. An outershoulder 188 may be defined by the interface of a portion of the outersurface 129 of the central body 182 and a step surface 132. The innerwidth 190 may be defined by a cylindrical inner shoulder surface 127intersecting normally with the step surface 132 and transitioning to anadditional radially oriented step surface 128. The width of the stepsurface 132 may define the difference between a diameter of acylindrical inner shoulder surface 127 and the diameter of the centralbody. The diameter of the inner shoulder surface 127 is less than thediameter of the central body 182 but larger than the diameter of thedistal extension 186. The width of the additional step surface 128 maydefine the difference between the diameter of the inner shoulder surface127 and the diameter of the distal extension 186.

The distal tip of the distal extension 186 may include a tapered orchamfered tip 189 creating a conical shape for receiving a dilatedportion 126 of the insulator tubing 124. As shown in FIG. 2, forexample, the dilated portion 126 of the insulator tubing 124 may bestretched, expanded, or otherwise distended over the distal extension186 of the connector insulator 116. The dilated portion 126 is held awayfrom the crimp connection of the inner conductor 120 to provide spacefor this connection and may help to avoid binding, pinching, orotherwise constricting the crimp connection at this location.

The proximal extension 184 of the connector insulator 116 may extendfrom the proximal end of the central body 182 and may be substantiallycylindrical with a diameter smaller than that of the central body 182.The transition between the central body 182 and the proximal extension184 may define a proximal shoulder 183 opposite the cascading shouldersdescribed. The interface between the proximal extension 184 and theproximal shoulder 183 may be formed as a small, concave, annular radius185. The outer surface of the proximal extension 184 may be formed as aplurality of alternating flat annular ribs 181 and flat annular channels187. The proximal extension 184 may extend underneath the proximal seal114. As such, when the proximal seal 114 is positioned on the proximalextension 184, a distal end of the proximal seal 114 may abut theproximal shoulder 194 of the central body 182 and a proximal end of theproximal seal 114 may align with the proximal end of the connectorinsulator 116.

The connector insulator 116 may include center bore 118 with a diameterconfigured for receiving the bar portion 164 of the connector pin 112.The diameter of the bore 118 may be slightly larger than the bar portion164 so as to allow rotation of the connector pin 112 relative to theconnector insulator 116. In other embodiments lubrication and/or abushing may be provided to offer further rotational freedom of the pin112 relative to the connector insulator 116. The center bore 118 mayextend from the proximal end of the insulator 116 to a point within thecentral body 182 of the insulator 116 where the center bore 118 maytransition to a bore 119 with a larger diameter. The bore 119 with thelarger diameter may accommodate the increased diameter of the conductorend 162 of the connector pin 112. The diameter of the bores 118, 119 mayremain slightly larger than the respective portion of the connector pin112. The bore 119, with its larger diameter, may extend through theremaining portion of the central body 182 and through the distalextension 186 of the connector insulator 116.

The connector insulator 116 may be constructed from a bio-compatiblegrade of insulator material. This material may be selected to providesufficient mechanical strength, elasticity, and insulationcharacteristics. For example, as described with respect to the connectorpin 112, the conductor end 162 of the connector pin 112 may be pressedthrough the bore 118 of the connector insulator 116. As such, theconnector insulator 116 may be made of a relatively strong yet elasticmaterial allowing the pin 112 to be driven therethrough without loss ofstrength and without permanent deformation. In some embodiments, theconnector insulator 116 may be made from a moldable thermoplastic suchas polyurethane, polysulfone, or PEEK. Still other material may beselected to provide the suitable strength, elasticity, and insulationcharacteristics.

While elastic, the connector insulator 116 may also be designed tosecure the connector pin 112 and prevent the connector pin 112 frombeing removed or withdrawn from the proximal end of the lead 100. Aproximal shoulder 131 at the proximal end of the conductor end 162 maybe provided to transition to the smaller diameter bar portion 164 (SeeFIG. 3.). A surface 135 of the shoulder 131 may interact with anopposing surface 137 of shoulder 133 on the interior surface of theconnector insulator 116. (See FIG. 2.) The shoulder 133 on the interiorof the connector insulator 116 may be formed as the transition betweenthe bore 118 and bore 119. The relative diameters of the bar portion 164and bore 118 and the relative diameters of the conductor end 162 andbore 119 may be selected to allow the connector pin 112 to rotate withinthe connector insulator 116. However, to prevent removal therefrom, thediameter of the conductor end 162 may be selected to be larger than thediameter of the bore 118. In addition, the material of connectorinsulator 116 may be selected to be rigid enough to prevent withdrawalof the connector pin 112 under withdrawal loads or strengths specifiedby the IS-1 specification, for example.

The proximal seal 114 may be configured for secured placement on theconnector insulator 116 and for sealingly engaging a socket on anelectrical stimulation device. In addition, the proximal seal 114 mayfunction, together with the connector insulator 116, to electricallyisolate and prevent crosstalk between the ring connector 130 and theconnector pin 112. As shown in FIGS. 6A and 6B, the proximal seal 114may include a flush portion 198 and a seal portion 199. The flushportion 198 may be distal to the seal portion 199 and may function toencompass the proximal extension 184 of the connector insulator 116 andabut the central body 182 thereof. The flush portion 198 may besubstantially cylindrical with an outer diameter substantially matchingthe outer diameter of the central body 182 of the connector insulator116 thereby being flush therewith. The seal portion 199 may be proximalto the flush portion 198 and may also be substantially cylindrical withan outer diameter slightly larger than the flush portion 198. The sealportion 199 may include one or more (e.g., two) annular,radially-extending ribs 196 protruding from the outer surface of theseal portion 199 and defining relatively deep channels 195 in between.The ribs 196 may extend from the seal portion 199 such that the outersurface or tip of the ribs 196 defines a diameter larger than the flushportion 198. The diameter of the channels 195 may be smaller than thediameter of the flush portion 198 such that there is a stepped shoulder195 between a base wall 193 of the channel 195 and the flush portion198. A proximal annular lip 191 of the proximal seal 114 may have asimilar diameter to the diameter of the channels 195 at the base wall193 and may extend proximally as an annular ring from the most proximalrib 196. The ribs 196 may be adapted to engage a cylindrical socket andmay have an outer diameter at least slightly larger than the diameter ofthe socket so as to sealingly engage an inner surface of the socket andprevent fluids or other matter from traveling into the socket andreaching the connector pin 112 or otherwise leaking into the electricalstimulation device.

The proximal seal 114 may include a bore 150 of constant diameterextending from the proximal end to the distal end. The bore 150 may besized to seal against the outer diameter of the proximal extension 184of the connector insulator 116. The diameter of the bore 150 may besubstantially equal to the outer diameter of the proximal extension 184of the connector insulator 116. The inner surface 156 of the bore 150may further be fixed to the proximal extension 184 of the connectorinsulator 116 by a medical adhesive or other bio-adaptable adhesiveequivalent.

In some embodiments, the proximal seal 114 may be made of a resilientmaterial and the diameter of the bore 150 may be slightly smaller thanthe outer diameter of the proximal extension 184 of the connectorinsulator 116 such that the proximal seal may be stretched to receivethe connector insulator 116 thereby compressively receiving theconnector insulator 116 therein. The proximal seal 114 may be made froma suitably resilient material to compressively seal the proximal end 102of the lead 100 with the electrical stimulation device. In someembodiments, the seal 114 may be a biocompatible silicone, for example.Still other materials may be selected to suitably seal the proximal end102 of the lead 100 with the electrical stimulation device and also becompatible with the body.

The insulator tubing 124 shown in FIG. 2 may function to electricallyisolate portions of the inner parts from the outer parts. Along someportions of the lead 100, the insulator tubing 124 may function togetherwith the connector insulator 116 to provide the electrical isolation. Asshown, conductive portions of each of the inner parts, including theconductor end 162 of the connector pin 112, the inner coil 120, and thepin sleeve 122, may be separated from the outer parts by the innerinsulator tubing 124. Near the proximal end of the conductor 120, thedistal extension 186 of the connector insulator 116 also isolates theseelements. The insulator tubing 124 may be substantially tube-like inshape defining an inner lumen having a diameter slightly larger than theouter diameter of the inner conductor or coil 120. As such, in the caseof an active lead, the inner conductor 120 may be relatively free torotate within the insulator tubing 124. The insulator tubing 124 may bemade of an insulating material so as to electrically isolate theenclosed components or features from the components or features outsidethe tubing 124.

The insulator tubing 124 may include a flared portion 126 at itsproximal end for receiving the distal extension 186 of the connectorinsulator 116. In some embodiments, the flared portion 126 is expandedto fit over the distal extension 186 of the connector insulator 116. Theflared portion 126 may be held open by the distal extension 186 of theconnector insulator 116 and may help to prevent binding of the innerparts by providing space for the crimp connection. Within the distalextension 186 of the connector insulator 116, the conductor end 162 ofthe pin connector 112, the pin sleeve 122, and the proximal end of theconductor or coil 120 may be arranged and thus electrically isolatedfrom components or features outside the portion 126.

Having described the inner parts and the isolation thereof by theinsulator tubing 124 and the connector insulator 116, the outer partsmay now be described. As shown in FIG. 2, the outer parts may includethe ring connector 130, an outer conductor or coil 134, and a ringsleeve 136.

The ring connector 130 may be configured to provide an exposed surfacefor electrical communication with an electrical stimulation device. Thering connector 130 may also be configured for axially and rotationallysecuring the outer parts to the connector insulator 116.

An isolated view of the ring connector 130 is shown in FIGS. 7A and 7B.The ring connector 130 may include a band portion 204, a slot portion206, and a crimp portion 208. The band portion 204 may form an exposedconductive band near the proximal end 102 of the lead 100 that is distalto the connector pin 112. The band portion 204 may be configured forelectrical communication with a portion of a socket of an electricalstimulation device and the diameter of the band portion 204 may beselected to suitably engage electrical conductors within the socket.

The band portion 204 may be substantially cylindrical in shape with anouter diameter matching that of the central body 182 of the connectorinsulator 116. The band portion 204 may define an inner cavity 210configured to receive the distal extension 186 of the connectorinsulator 116. More particularly, the inner cavity 210 of the bandportion 204 may have a diameter substantially equal to or slightlysmaller than the outer diameter of the cylindrical inner shouldersurface 127 on the connector insulator 116. As such, the band portion204 may be sleeved over the flared portion 126 positioned on the distalextension 186 and may frictionally engage the cylindrical inner shouldersurface 127 to secure the ring connector 130 to the connector insulator116. Additionally or alternatively, the band portion 204 may be bondedto the cylindrical inner shoulder surface 127 with medical adhesive. Theband portion 204 may include internal threading 211, as shown in FIGS.7C and 7D, to increase a bonding area between the band portion 204 ofthe connector insulator 116 and the cylindrical inner shoulder surface127 of the ring connector 130, thereby increasing the strength of thebond between the parts. In this manner, the concentric assembly of theseveral parts of the system may be maintained. The proximal edge of theband portion 204 of the ring connector 130 may thus abut the stepsurface 132 of the connector insulator 116 causing the outer surface ofthe band portion 204 to be flush with the central body 182 of theconnector insulator 116. The band portion 204 may have a length slightlygreater than the length of the distal extension 186 of the connectorinsulator 116.

The slot portion 206 of the ring connector 130 is distal relative to theband portion 204 and is positioned intermediate the band portion 204 andthe crimp portion 208. The slot portion 206 may be substantiallycylindrical in shape with a diameter smaller than the band portion 204.The slot portion 206 may have an inner diameter similar to or slightlylarger than the outer diameter of the insulator tubing 124, whereby theslot portion 206 is configured to engage in a tight fit with theinsulator tubing 124. The outer diameter of the slot portion 206 mayallow for an inwardly projecting rib 143 from the boot seal 140 to nesttherein as further described below. The rib 143 may be held in positionlongitudinally by two opposing surfaces 242 and 243 defining theboundaries of the slot portion 206. The slot portion 206 may include oneor more holes 214 for introduction of adhesive to secure the ringconnector 130, the insulator tubing 124, and the boot seal 140 together.

The crimp portion 208 may be arranged distally to the slot portion 206and may be substantially cylindrical in shape with an outer diameterlarger than the slot portion 206 and smaller than the band portion 204.Like the conductor end 162 of the connector pin 112, the crimp portion208 of the ring connector 130 may be configured for crimping of theouter conductor 134 therein. As such, the crimp portion 208 may define acrimp zone or cavity 216 therein. The cavity or crimp zone 216 mayinclude an inner diameter selected in conjunction with the ring sleeve136 to suitably crimp the outer conductor 134 therein. That is, the ringsleeve 136 may have an outer diameter and the outer conductor 134 mayinclude a wire thickness. The inner diameter of the crimp zone or cavity216 may be selected to be equal to or slightly smaller than the outerdiameter of the ring sleeve 136 plus twice the wire thickness, forexample.

Like the inner conductor crimp connection, the material strength,diameter, thickness, and elasticity may be considered when selecting therelative diameters for crimping the outer conductor 134. The crimpportion 206 of the ring connector 130 may have a length equal to orslightly larger than the ring sleeve 136 such that a sufficient lengthof the outer conductor 134 may be crimped therein. In some embodimentsthe crimp portion 208 of the ring connector 130 may includecircumferentially extending grooves 218 extending around itscircumferential outer surface for engagement with the boot seal 140. Thecrimp portion 208 may also include a hole or a pair of holes 220 forinspecting the crimped conductor 134 within the cavity 216 andconfirming the quality of the connection. The holes 220 may extendthrough the crimp portion 208 from an outer surface and into the cavity216 and may be positioned near a proximal end of the cavity 216. Assuch, when the conductor 134 is crimped in the cavity 216, a portion ofthe conductor 134 may be visible through the hole or holes 220 and thecrimp connection may be ascertainable to assure sufficient crimp length.

Like the connector pin 112, the ring connector 130 may be constructed ofa bio-compatible conductive material. For example, the ring connector130 may be made from stainless steel 316L or a metal alloy MP35N. Othermaterials may also be used and may be selected to provide suitablebiocompatibility and conductivity. Additionally, as with the connectorpin 112, the material and dimensions (e.g., relative diameters and wallthicknesses) may be selected to suitably allow for a crimp connection tothe outer conductor or coil 134 that is both mechanically secure andalso effectively transmits electrical signals.

The outer conductor or coil 134 may be the same or similar to the innerconductor or coil 120. However, the outer conductor or coil 134 has adiameter larger than the inner conductor or coil 120. The diameter ofthe outer conductor or coil 134 may be selected such that the innerconductor or coil 120 and the insulator tubing 124 may be receivedtherein. As such, the outer conductor or coil 134 may have a diameterequal to or slightly greater than an outside diameter of the innerconductor or coil 120 plus twice the thickness of the insulator tubing124. In some embodiments, the diameter of the outer conductor or coil134 may be selected to allow non-constricted rotation of the inner coil120 within the insulator tubing 124 for controlling an active mechanism106 on a distal end 104 of the lead 100, for example. In otherembodiments, the diameter of the outer coil 134 may be more constrictingon the insulator tubing 124 and the inner coil 120.

The ring sleeve 136, like the pin sleeve 122 may be configured forcrimping the outer conductor or coil 134 within the crimp portion 208 ofthe ring connector 130. As shown in FIGS. 8A and 8B, the ring sleeve 136may be formed as a cylindrical sleeve portion 222 with a flare or flangeportion 224 for controlling the depth within the coil 134 that the ringsleeve 136 extends. The sleeve portion 222 may be substantiallycylindrical with an outer diameter slightly larger than an innerdiameter of the outer coil 134. As such, when inserted into a proximalend of the outer coil 134, some frictional engagement between the ringsleeve 136 and the outer coil 134 may be provided. The flare or flangeportion 224 may be positioned on the proximal end of the sleeve portion222 and may have an outer diameter larger than that of the sleeveportion 222 for abutting the end of the outer conductor or coil 134 andresisting advancement of the ring sleeve 136 beyond the proximal end ofthe outer conductor or coil 134. The diameter of the flare or rib 224may be selected to be slightly less than the inner diameter of the crimpportion 208 of the ring connector 130 so as to avoid inhibiting thepinching or crimping of the coil 134 between the sleeve portion 222 andthe inner surface of the crimp portion 208 of the ring connector 130. Asdiscussed with respect to the pin sleeve 122, the shape of the proximalend of the pin sleeve 122 and the ring sleeve 136 may depend in part onthe type of raw material used to form the respective part. For example,if tubing is used, the proximal end may be flared, while, if bar stockis used, the proximal end may be more square in cross-section orflange-like. Other geometries may also be provided to stop the sleevesfrom advancing too far into the proximal end of the respective coils120, 134.

The boot seal 140 is shown in FIGS. 9A and 9B. The boot seal 140 may beconfigured for encompassing and sealing against the distal end of thering connector 130 and the proximal end of the outer sheath 152 toprevent entry of fluids. For example, when the proximal end 102 of thelead 100 is inserted into a socket of an electrical stimulation device,the boot seal 140 may prevent fluids or other material from entering thesocket and interfering with the ring connector 130 or other portions ofthe electrical stimulation device. As such, the boot seal 140, like theproximal seal 114, may have one or more annular, radially-extendingsealing ribs 144 protruding from its outer surface at its proximal end.The sealing ribs 144 may be adapted to engage a cylindrical socket andmay have an outer diameter at least slightly larger than the diameter ofthe socket so as to sealingly engage an inner surface of the socket andprevent fluids or other matter from traveling into the socket andreaching the ring connector 130 or otherwise leaking into the electricalstimulation device. The boot seal 140 may be relatively long with acylindrical shaft portion 142 that extends distally from the sealingribs 144 and may provide a grip for the surgeon or other installer forhandling the proximal end 102 of the lead 100. The cylindrical shaftportion 142 may taper radially inward at the distal end of the boot seal140 to form a chamfered portion 148.

The boot seal 140 may define a bore 141 extending from its proximal endto its distal end. The diameter of the bore may vary along the length ofthe seal 140. The diameter of a proximal section 145 of the bore 141 maybe sized to house the crimp portion 208 of the ring connector 130.Moving distally, the diameter of the bore 141 throughout a medialsection 146 may be reduced and may be sized just slightly larger thanthe outer diameter of the outer coil 134. Moving still further distally,the diameter of a distal section 147 of the bore 141 may again beenlarged with respect to the medial section 146. In this distal boresection 147, the boot seal 140 may be enlarged to receive the outerinsulating sheath 152 and for the application of a lead label and/orserial number. The bore 141 within the chamfered portion 148 at thedistal end of the boot seal 140 may also be tapered slightly radiallyinward to form a tapered seal portion 149 that creates the fluid tightseal around the outer sheath 152. The proximal end of the boot seal 140may define an annular securing rib 143 protruding inwardly forpositioning in the slot portion 206 of the ring connector 130, therebysecuring the axial position of the boot seal 140. Like the proximal seal114, the boot seal 140 may be made from a biocompatible silicone toresiliently engage and seal the lead 100 relative to the electricalstimulation device. Other materials may also be used.

Referring again to FIG. 2, the assembled proximal end of the lead may bedescribed. As shown, the electrically conductive connector pin 112 mayextend through and may be rotatably disposed in a center bore 150 of aproximal seal 114 and a center bore 118 of a connector insulator 116.The bar portion 164 of the connector pin 112 may be arranged in thecenter bore 118 of the connector insulator 116. The bar portion 164 maybe separated from the inner surface of the center bore 150 by theproximal extension 184 of the connector insulator 116. As such, an innersurface 154 of the connector insulator 116 may provide rotationalbearing for the connector pin 112 such that the connector pin 112 mayrotate relative to the connector insulator 116 and proximal seal 114.Rotation of the connector pin 112 may drive rotation of the inner coil120, thereby rotating the helical anchor electrode 108 of the activeelectrode tip 106 disposed at the distal end 104 of the lead 100. It isappreciated that other suitable rotatable connection structures may beused between the inner coil 120 and the connector pin 112.

The electrically conductive inner conductor or coil 120 may be crimpedto the conductor end 162 of the connector pin 112 in conjunction withthe pin sleeve 122. The inner insulator tubing 124 may extend over theinner coil 120 and the flared portion 126 thereof may be sleeved ontothe distal extension 186 of the connector insulator 116 to abut theinner shoulder 190 of the cascading shoulders and having an outersurface substantially flush with the cylindrical outer surface 127 ofthe inner shoulder 190. As such, the connector pin 112, the crimpconnection, and the inner coil 120 may be substantially fully insulatedalong its length by the connector insulator 116 and the insulator tubing124. However, the inner conductor 120 may be exposed via an electrode atthe distal end 104 for treatment and the connector pin 112 may beexposed at the proximal end 102 for electrical communication with anelectrical stimulation device. The proximal seal 114 may be arranged onthe connector insulator 116 and the outwardly projecting ribs 196 mayengage a socket on an electrical stimulation device to prevent fluid orother liquid from contacting with the connector pin 112.

The band portion 204 of the ring connector 130 may extend over theflared portion 126 of the insulator tubing 124 and may abut the outershoulder 188 of the cascading shoulders on the connector insulator 116.As shown, the outer surface of the band portion 204 of the ringconnector 130 may be flush with the outer surface 129 of the centralbody 182 of the connector insulator 116. The outer conductor or outercoil 134 may be arranged to sleevably receive the inner coil 120 andinsulator tubing 124. The outer conductor or coil 134 may be crimped tothe ring connector 130 by a ring sleeve 136, thereby electricallyconnecting to the ring connector 130. The boot seal 140 may bepositioned over the outer coil 134 and an inwardly protruding rib 143thereof may engage a slot portion 206 of the ring connector therebysecuring the position of the boot seal 140 relative to the ringconnector 130. The crimped outer coil 134 and portions of the ringconnector 130 may be disposed within a center bore 141 of the boot seal140. Like the proximal seal 114, the radially projecting ribs 144 of theboot seal 140 may engage a socket on an electrical stimulation device toprevent body fluid or other liquid from contacting the ring connector130 or otherwise entering the electrical stimulation device.

Accordingly, the connector pin 112 may be electrically connected to theinner coil 120, and the ring connector 130 may be electrically connectedto the outer coil 134. In operation of the lead100, electrical signalsmay be sent from the proximal end 102 to the distal end 104 via theconnector pin 112 and the inner coil 120, and via the ring connector 130and the outer coil 134. The inner coil 120 may be electrically insulatedfrom the outer coil 134 by the inner insulator tubing 124. The ringconnector 130 may be electrically insulated from the inner coil 120 bythe inner insulator tubing 124 and the connector insulator 116. Theconnector pin 112 may be electrically insulated from the ring connector130 by the proximal seal 114 and the connector insulator 116. Theconnector pin 112 may be prevented from contacting fluid or other liquidby the sealing ribs 196 of the proximal seal 114. The ring connector 130may be prevented from being in contact with fluid or other liquid by thesealing ribs 144 of the boot seal 140.

The active electrode tip 106 at the distal end 104 of the lead 100 isdepicted in FIG. 10A and in cross section in FIGS. 10B and 10C. Theactive electrode tip 106 may be considered to be composed of severalprimary components: a ring electrode 103, a tip electrode pin 105, ahelical anchor electrode 108, an intermediate connection mount 109, atip housing 110, and a soft tip plug 117. Additional components mayinclude a marker band 111, a spacer/stopper 113, and a distal seal 115 Aproximal end of the ring electrode 103 is electrically and mechanicallyconnected to the distal end of the outer conductor coil 134. Theproximal end of the tip electrode pin 105 is electrically andmechanically connected to the distal end of the inner conductor coil120. The distal end of the tip electrode pin 105 is connected to theproximal end of the helical anchor electrode 108. The intermediateconnection mount 109 connects the ring electrode 103 to the tip housing110 to form an outer surface of the active electrode tip 106. Theproximal portion of the tip electrode pin 105 and the helical anchorelectrode 108 are substantially encased within the tip housing 110 whenthe helical anchor electrode 108 is in a retracted state. When thehelical anchor electrode 108 is advanced as shown in FIG. 10C andfurther described below, the distal tip of the helical anchor electrode108 protrudes beyond the soft tip plug 117 in the distal end of the tiphousing 110.

An exemplary embodiment of the tip electrode pin 105 is depicted ingreater detail in FIGS. 11A and 11B. The tip electrode pin 105 may bemade of a solid conducting material and is generally cylindrical inshape with a number of shaft sections separated by a number of annularflanges. The tip electrode pin 105 may be made, for example, ofstainless steel (e.g., 316L), a precious metal (e.g., platinum oriridium), or a metal alloy (e.g., Pt/Ir or MP35N), or anotherelectrically conductive, biocompatible material. At the proximal end, aproximal shaft section 302 of a first diameter is provided. The proximalshaft section 302 is the section of the tip electrode pin 105 thatengages the inner conductor coil 120 as will be described in furtherdetail below. The proximal shaft section 302 transitions at a squaredshoulder to a larger diameter annular step 303. At the distal edge ofthe annular step 303, an angled annular wall 305 gradually increases indiameter from the annular step 303 until it intersects a proximal faceof a proximal annular flange 307 that functions as a proximal stopfeature as further described below. The proximal annular flange 307 iscylindrical and has an outer diameter that is greater than the largestdiameter of the angled annular wall 305.

A medial shaft section 304 may be substantially the same diameter andlength as the proximal shaft section 302 extends distally from theproximal annular flange 307 and terminates upon intersecting with aproximal face of a medial annular flange 310 that functions, in part, asa distal stop feature as further described below. The medial annularflange 310 is cylindrical and may have an outer diameter that is greaterthan the inner diameter of the spacer/stopper ring 113. The medialannular flange 310 may transition distally into a seal shaft section 306about which a seal ring 115 may be fitted as shown in FIG. 10B and asfurther described below. The seal shaft section 306 may be ofsubstantially the same diameter as each of the proximal and medial shaftsections 302, 303, but of a substantially shorter length. The seal shaftsection 306 may further transition into a cylindrical distal annularflange 312 that is of both a greater outer diameter and a greaterlongitudinal thickness than the medial annular flange 310. The distalannular flange 312 further transitions into a distal shaft section 308that is of a greater diameter than the prior shaft sections, but of asmaller diameter than each of the annular flanges. The distal shaftsection 308 of the tip electrode pin 105 is the part that directlyconnects with the proximal end of the helical anchor 108. The distal endof the distal shaft section 308 may have a chamfered edge as shown inFIG. 11 that transitions into a flat tip face 311. The distal shaftsection 308 and the distal annular flange 312 may be exposed to thepatient's blood when the lead 100 is implanted in vivo.

An exemplary embodiment of the helical anchor 108 is depicted inisolation in FIG. 12 and in conjunction with the tip electrode pin 105in FIG. 13. The helical anchor 108 acts as both a conductor and as afixation structure to anchor the lead 100 into the endocardium within achamber of the heart. The helical anchor 108 may be made of a solidconducting material, for example, a Platinum/Iridium alloy or anotherstrong, electrically-conductive, biocompatible material formed in a coilshape, with sufficient strength to penetrate into the heart tissue andfix the lead 100 in position for sensing and pacing. The helical anchor108 may have a proximal connecting section 314, a helical section 316,and a distal end 318. The proximal connecting section 314 may be formedwith a close winding 315 at the proximal end where the terminal end ofthe first winding is adjacent to and in contact with the beginning ofthe second winding before the windings begin to space apart in a helicalshape. The close winding 315 in the proximal connecting section 314provides for a sufficient surface area contact between the helicalanchor 108 and the tip electrode pin 105 to form a strong weldedconnection as discussed below. The helical section 316 extends distallyfrom the proximal connecting section 314 and the windings in thissection take on a helical form. The helical anchor 108 terminates at thedistal end 318 in a sharp tip 317 that is able to penetrate and lodgewithin the endocardial tissue when the helical anchor 108 is rotatedlike a corkscrew and advances distally out of the active electrode tip106.

Although not depicted in FIG. 13, the steroid capsule 107 shown in FIGS.10B and 10C may be placed within the lumen of the helical anchorelectrode 108. The steroid capsule 107 may be formed as a cylindricalplug sized to fit snugly within the helical anchor electrode 108. Thesteroid capsule 107 may be any of a number of steroids (e.g.,dexamethasone) or medicaments prepared in a binder for timed releaseafter implantation of the lead 100 in order to promote healing of anytrauma caused by placement of the lead 100 or to deliver a desirabledrug for efficacy within the heart. The steroid capsule 107 may beadhered within the windings of the helical anchor electrode 108 with abiocompatible adhesive to ensure that the steroid capsule 107 does notdislodge before completely eluting.

The proximal end of the tip electrode pin 105 is positioned within theintermediate connection mount 109, which is depicted in isolation inFIGS. 14A and 14B. The intermediate connection mount 109 may beunderstood as a tube-like structure having three primary sections: aproximal fitting 370, a distal fitting 374, and a medial separator 372located between the proximal and distal fittings 370, 374. Theintermediate connection mount 109 defines an axial lumen therethroughfrom the proximal end to the distal end. The proximal fitting 370 isconfigured to receive the distal end of the insulating tubing 124surrounding the inner conductor coil 120. The proximal fitting 370 isformed with a tapered slope 371 on the outer diameter thereof increasingin diameter as the tapered slope 371 extends distally. The tapered slope371 then transitions into a first of two arcuate channels 375 separatedfrom each other by an arcuate ridge 373. The arcuate ridge 373 may bedesigned to have substantially the same outer diameter as the distalterminus of the tapered slope 371 while the outer diameter of the baseof the arcuate channels 375 is less than the outer diameter of thearcuate ridge 373. The distal arcuate channel 375 transitions into aproximal landing 377 that is an annular surface with substantially thesame diameter as the diameter of the arcuate ridge 373.

The proximal landing 377 interfaces with a proximal abutting surface379, which is essentially a square shoulder of the medial separator 372,which is formed as a large cylindrical flange 380 with a flat, annularouter surface. The distal side of the cylindrical flange 380 may alsoform a square shoulder that provides a distal abutting surface 381 thatintersects with a distal landing 382, which is a smooth, annular surfaceadjacent the cylindrical flange 380. The outer diameter of the distallanding 382 may be substantially the same as the outer diameter of theproximal landing 377. The distal landing 382 begins the distal fitting374 of the intermediate connection mount 109. A plurality of alternatingshallow channels 385 of arcuate cross section and flat ribs 383 ofsubstantially the same diameter as the distal landing 382 form themajority of the rest of the distal fitting 374 until a tip landing 386is reached. The tip landing 384 may have a smooth, annular, outersurface and may be of substantially the same outer diameter as each ofthe distal landing 382 and the flat ribs 383. The tip landing 384 maytransition to an annular chamfered tip 386 that further transitions intoa flat face 387 at the distal end.

The lumen within the intermediate connection mount 109 may be formed intwo parts, a proximal lumen 376 and a distal lumen 378. The proximallumen 376 may be of smaller inner diameter than the distal lumen 378. Achamfered step 388 within the sidewall of the lumen may be used totransition from the narrower proximal lumen 376 to the wider distallumen 378.

An exemplary embodiment of the ring electrode 103 is depicted in greaterdetail in FIGS. 15A and 15B. The ring electrode 103 is generally tubularin shape with various cylindrical sections of varying diameter. Asmooth, cylindrical proximal sleeve 350 forms the proximal end of thering electrode 103 and is sized in length and diameter to fit within thedistal end of the outer connecter coil 134 and may be laser weldedthereto or otherwise securely mechanically attached to form a permanentmechanical and electrical connection. The proximal end of the proximalsleeve 350 may be formed with a proximal chamfered edge 367 thattransitions to a proximal flat face 368. An adhesive channel 352 isformed distally adjacent the proximal sleeve 350 and is defined by aproximal curb 351 and a distal curb 353. The proximal curb 351 and thedistal curb 353 may be of the same diameter, which may be slightlylarger in diameter than the proximal sleeve 350. The adhesive channel352 may be substantially the same diameter as the proximal sleeve 350.The proximal curb 351 may separate the proximal sleeve from the adhesivechannel 352. The diameters of the proximal and distal curbs 351, 353 areselected to be substantially the same as the inner diameter of the outersheath 152 and the surfaces of the proximal and distal curbs 351, 353are smooth in order to provide a friction fit with the outer sheath 152.The adhesive channel 352 may define one or more adhesive apertures 354(two are shown in the exemplary embodiment) in order to introduce abiocompatible adhesive into the channel 352 to bond the ring electrode103 to the outer sheath 152.

The ring electrode 103 may transition from the adhesive channel 352 viaa proximal shoulder 355 adjacent the distal curb 353 to an exposedsection 356 of a greater outer diameter. The exposed section 356 issmooth and cylindrical in shape and is not covered or insulated from thepatient's blood or tissue. The ring electrode 103 may be made ofstainless steel (e.g., 316L), a precious metal (e.g., platinum oriridium), or a metal alloy (e.g., Pt/Ir or MP35N), or anotherelectrically conductive, biocompatible material. The exposed section 356may be coated with TiN to increase the surface area and thereby achievea better sensing signal. The distal end of the exposed section 356transitions with a distal chamfered edge 357 to terminate at a distalflat face 360.

The ring electrode 103 may also define a lumen of two different boresizes. A proximal bore 362 is sized to be of a slightly larger diameterthan the insulating tubing 124 surrounding the inner conductor coil 120to provide clearance for its passage therethrough. A distal bore 364 issized to be slightly larger than proximal fitting 370 of theintermediate connection mount 109 to surround the outer diameter of theinsulating tubing 124 sleeved thereon. While the proximal bore wall 366is smooth, the wall of the distal bore 364 may be formed with a seriesof flat annular ribs 358 separated from each other by a series ofgrooved annular channels 359. A smooth annular landing 361 is formedwithin the distal bore 364 proximally adjacent the last grooved annularchannel 359. An angled wall 363 is formed proximally adjacent theannular landing 361 to provide the transition to the smaller diameter ofthe proximal bore 362. A pair of adhesive canals 365 is formed withinthe proximal bore wall 366 between each of the adhesive apertures 354and the angled wall 363. The adhesive canals 365 are thus recessed areaswithin the proximal bore wall 366 that also result in a lower height ofthe angled wall 363 at its intersection with the proximal bore 362 atthe locations of the adhesive canals.

FIG. 16 depicts the spacer/stopper ring 113 that fits around the distalportion of the tip electrode pin 105 beyond the distal end of theintermediate connector mount 109. The spacer/stopper 113 may be formedas a C-shaped body 390 of generally cylindrical form, but that defines acylindrical aperture 391 aligned along the center axis and a gap 392 inthe otherwise annular wall to form the C-shape. The gap 392 allows thespacer/stopper 113 to be easily placed about the medial shaft section304 of the tip electrode pin 105 adjacent the medial annular flange 310.The spacer/stopper ring 113 may be made of a material that is flexibleand resilient enough to allow the gap 392 to be enlarged to fit aroundthe medial shaft section 304 during assembly and then return to itsoriginal size and C-shape. The cylindrical aperture 391 is thussubstantially the same diameter as the outer diameter of the medialshaft section 304 so that it can easily seat thereon. The gap 392 shouldbe narrower than the outer diameter of the medial shaft section 304 suchthat once the spacer/stopper 113 is placed on the medial shaft section304, it will not slide off.

FIGS. 17A and 17B depict an exemplary embodiment of the seal ring 115 inisolation. The seal ring 115 is formed as a generally annular body 394defining a lumen axially therethrough. The seal ring 115 may be made ofan elastomeric material that is flexible and resilient enough to fitover the distal shaft section and the distal annular flange 312 of thetip electrode pin 105 such that the seal ring 115 can seat about theseal shaft section 306 on the tip electrode pin 105. The annular body394 has a flat proximal face 395 and a flat distal face 397 and a curvedradial wall 393. The outer diameter at the edge of the distal face 397and the radial wall 393 is larger than the outer diameter at the edge ofthe proximal face 395 and the radial wall 393. Thus, the outer diameterof the annular body 394 decreases from the distal face 397 to theproximal face 395 following the curve of the radial wall 393. The distalface 397 also transitions from a flat surface to a radius entrance 398to the lumen. The radius entrance 398 transitions to a cylindricalsection 399 part way through the lumen and maintains the cylindricalform until the lumen exits the proximal face 395

An exemplary embodiment of the tip housing 110 is depicted in greaterdetail in FIGS. 18A and 18B. The tip housing 110 may be generallycylindrical in shape with a long tubular sheath 324 of a substantiallyconstant outer diameter along its length. The tubular sheath 324 maydefine an axial lumen therethrough from the proximal end to the distalend. Two retention apertures 330 may be formed through the wall of thetubular sheath 324 adjacent the distal end and at symmetrically oppositelocations thereon. The tip housing 110 may be formed of a resilientbiocompatible material (e.g., polyether ether ketone (PEEK) orpolysulfone) in order to be fitted over the intermediate connectionmount and retained thereon.

At a proximal end, the lumen may define a sleeve bore 328 of relativelylarger diameter with respect to the rest of the lumen 326 that is sizedin both diameter and length to sleeve over and create a fluid-tightconnection with the distal fitting 374 of the intermediate connectionmount 109. The proximal end of the tubular sheath 324 may provide achamfered entrance 325 to the sleeve bore 328. The sleeve bore 328transitions at a squared sleeve shoulder 329 to a relatively long middlebore 332 of a narrower inner diameter that is sized to extend primarilyover the helical section 316 of the helical anchor electrode 108. Themiddle bore 332 also acts as a sealing section to form a fluid-tightseal with the seal ring 115 as further described below. An anchor guide336 protrudes from a wall of the middle bore 332 at the distal endthereof and extends radially inward into the lumen 326. The anchor guide336 may be sized to fit between adjacent windings of the helical anchorelectrode 108 and extend a distance slightly greater than a diameter(thickness) of the windings of the helical anchor electrode 108. Asshown in the exemplary embodiment, the anchor guide 336 is alignedlongitudinally with one of the retention apertures 330; however, it maybe located at any position about the circumference of the middle bore332.

The middle bore 332 may transition into a tip bore 338 of a larger innerdiameter via a stepped structure including a squared shoulder 333 thatincreases the lumen diameter slightly to an annular shelf 337, whichfurther transitions to a shelf shoulder 335 that ultimately extends thelumen radially to the diameter of the tip bore 338. The retentionapertures 330 described above are positioned within the tip bore 338 inthe lumen 326. Additionally, a pair of guide walls 334 extend into thetip bore 338 as extensions of the middle bore 332. The guide walls 334are arcuate in form, are symmetrically opposed from each other withinthe tip bore 338, may be generally rectangular in projection of theirperimeter boundaries, and a separation distance between opposing pointson the guide walls 334 is the same as the diameter of the middle bore332. The guide walls 334 are spaced apart from the wall of the tip bore338 by respective retention posts 331 centered on the outer sides of theguide walls 334. The retention posts 331 connect the guide walls 334 tothe wall defining the tip bore 338 and define the separation distancebetween the two. The retention posts 331 may be cylindrical in shape andspaced apart from the annular shelf 337 such that there is void space onall sides of the retention posts 331 between the guide walls 334 and thewall defining the tip bore 338. The retention posts 331 may be formed onthe inner wall of the tubular sheath 324 defining the tip bore 338symmetrically opposite each other and equidistant from the retentionapertures 330 such that there is a 90° separation between adjacentretention apertures 330 and retention posts 331.

An exemplary embodiment of a marker band 111 is shown in isolation inFIG. 19. The marker band 111 may be formed of a radiopaque material,e.g., a Pt/Ir alloy or a thermoplastic compound suitable forinjection-molding and having an opacity to X-rays more than sufficientto guarantee shielding comparable to that of a metal. The marker band111 provides a mark for a physician to identify under fluoroscopy thelocation of the distal end 104 of the active electrode tip 106 andallows the physician to determine whether the helical anchor electrode108 is at retracted position or extension position or in between bycomparing the position of the helical anchor electrode 108 to the markerband 111. The marker band 111 may be formed as an annular wall 320defining a cylindrical lumen 312. The outer diameter of the annular wall320 may be congruent with the inner diameter of the tip bore 338 of thetip housing 110 within which the marker band 111 resides and is formedas described further below. The thickness of the annular wall 320 issuch that the diameter of the cylindrical lumen 321 is congruent withthe diameter of the annular shelf 337. The annular wall 320 furtherdefines four sidewall retention holes 322 that are spaced 90° apart foralignment with respective ones of the retention posts 331 and retentionapertures 330 on the tip housing 110.

FIGS. 20A and 20B depict an exemplary embodiment of the soft tip plug117, which fits within and connects to the tip bore 338 of the tiphousing 110. The soft tip plug 117 may be formed of a molded,biocompatible, elastomeric material designed to minimize trauma tovasculature and tissue, including lead perforation, as the lead 100 ispositioned for implantation. In some embodiments, the soft tip plug 117may be coated with a steroid (e.g., dexamethasone) for relievinginflammation at the implant location or with other medicinal agents. Thesoft tip plug 117 may be composed of an exposed section 340 and aretention section 342 extending proximally from the exposed section 340.The exposed section 340 may be formed as a ring defining a tip lumen 344and defined by a smooth annular edge 341, a flat proximal face 349, aflat distal face 345, and a chamfered face 343 transitioning between theannular edge 341 and the distal face 345.

The retention section 342 of the soft tip plug 117 may be primarilycomposed of a pair of arcuate walls 346 a/b that extend proximally fromthe proximal face 349 of the exposed section 340. The arcuate walls 346a/be may be arranged symmetrically opposite each other about the tiplumen 344 and are separated at lateral edges by a pair of gaps 347 a/b.The tip lumen 344 may be of constant diameter through each of theexposed section 340 and the retention section 342. The outer diameter ofthe arcuate walls 346 a/b may be congruent with the inner diameter ofthe tip bore 338 such that the arcuate walls 346 a/b may be receivedwithin the tip bore 338. The diameter of the annular edge 341 may becongruent with the outer diameter of the tip housing 110 such that theexposed section 340 smoothly transitions into the tip housing 110. Apair of retention plugs 348 a/b may be formed on the outer surfaces ofrespective annular walls 346 a/b and extend radially therefrom to aheight congruent with the annular edge 341. The retention plugs 348 a/bare configured to fit within the retention apertures 330 in the tiphousing 110 to retain the soft ip plug 117 within the distal bore 330 ofthe tip housing 110.

Since the lead 100 is bipolar, two electrical connections must be madebetween the proximal end 102 and the distal end 104. The inner conductorcoil 120 and the outer conductor coil 134 provide the electricalconnection between the proximal end 102 and distal end 104 of the lead100. As shown in FIG. 10B, the inner conductor coil 120 fits over theproximal shaft section 302 of the tip electrode pin 105 to abut theannular step 303 and is laser welded circumferentially to the proximalshaft section. On the distal end of the tip electrode pin 105, thehelical anchor electrode 108 is place upon and also laser welded (e.g.,by spot welding) to the distal shaft section 108 to complete aconnection with the inner conductor coli 120 and provide an electricalimpulse current to the heart.

The proximal shaft section 302 of the tip electrode pin 105 andcorresponding connection with the inner conductor coil 120 reside withinthe proximal lumen 376 of the intermediate connection mount 109. Thediameter of the proximal lumen 376 is larger than the diameter of theinner conductor coil 120 when sleeved over the proximal shaft section302, thereby allowing the tip electrode pin 105 and attached innerconductor coil 120 to freely rotate within the proximal lumen of theintermediate connection mount 109. The angled annular wall 305 of thetip electrode pin 105 interfaces with the chamfered step 388 within theintermediate connection mount 109 to provide an axial alignmentinterface and opposing bearing surfaces to allow for rotation of theinner conductor coil 120 and the tip electrode pin 105 within theintermediate connection mount 109. The insulating tubing (e.g., silicon)covering substantially the entire length of inner conductor coil 120from the proximal end 102 of the lead 100 through the outer sheath 152may be expanded and flared upon reaching the tapered end 371 of theintermediate connection mount 109 to sleeve over the proximal fitting370 until it abuts the proximal abutting surface 379. A fluid-tightfriction fit is thus formed between the insulating tubing 124 and theproximal fitting 370 of the intermediate connection mount 109.Electrical insulation is thus provided between the inner conductor coil120 and the outer conductor coil 134 along the entire length of thelead.

The outer conductor coil 134 is designed to sleeve over the proximalsleeve 350 of the ring electrode 103 with mild radial expansion until itabuts the proximal curb 351 and is then laser welded circumferentiallyto the proximal sleeve, whereby electrical impulses from the heart canbe sensed by the ring electrode 103 and transmitted through the lead 100to a base unit for monitoring and processing. The diameter of theproximal bore 366 of the proximal sleeve 350 is larger than the diameterof the inner conductor coil 120 and the insulating tubing 125, therebyallowing the insulating tubing 124 and inner conductor coil 120 tofreely fit within and move proximally and distally as the helical anchorelectrode 108 is extended and retracted into and out of the distal tip106.

The exposed section of the ring electrode 103 is sleeved over the distalend of insulating tubing 124, which is stretched over the proximalfitting 370 of the intermediate connection mount 109. Medical adhesiveapplied within the adhesive apertures 354 may travel within the adhesivecanals 365 in the ring electrode 103 to flow along the outer surface ofthe insulating tubing 124 and within the threading (the annular ribs andgrooved channels 358, 359) of the distal bore 364. The medical adhesivebonds the ring electrode 103 to the insulating tubing 124 and therebythe to intermediate connector mount underneath. The threading in thedistal bore 364 increase the bonding area and thereby the strength ofthe bond with the insulating tubing 124. The outer sheath 152 is sleevedover the distal end of the outer conductor coil 134 and further over theproximal and distal curbs 351, 353 of the ring electrode 103 until itabuts the outer shoulder. Medical adhesive within the adhesive channelbetween the proximal and distal curbs 351, 353 bonds the outer sheath152 to the proximal end of the ring electrode 103.

In addition to the helical anchor electrode 108, the spacer/stopper ring113 and the seal ring 115 are mounted on the distal end of the tipelectrode pin 105 that extends distally beyond the distal fitting 374 ofthe intermediate connection mount 109. The spacer/stopper ring 113 isplaced about the medial shaft section 304 of the tip electrode pin 105adjacent the medial annular flange 310. The spacer/stopper 113 may bemade of an electrically insulating material to reduce potentialelectrode electrical “chatter” that is known to occur in prior artdesigns with metallic components used in the control of advancement andretraction. For example, the spacer/stopper 113 may be made ofpolyethylene, polyether ether ketone (PEEK), or polysulfone, and mayhave a hardness of Shore 80 in order to provide appropriate flexibilityto fit around the medial shaft section 304 and appropriate resiliency tobe retained thereon. The diameter of the spacer/stopper 113 is slightlyless than the inner diameter of the tip housing 110 in which it and thehelical anchor electrode 108 are ultimately housed. In this manner, asthe helical anchor electrode 108 is advanced out of and retracted intothe tip electrode 106, the spacer/stopper 113 can slide within thesleeve bore 328 of the tip housing 110 and around the medial shaftsection 304 of the tip electrode pin 105 while helping maintain axialalignment of the helical anchor electrode 108 within the tip housing110.

The distal and proximal travel of the helical anchor electrode 108 islimited by the spacer/stopper 113 in combination with the proximalannular flange 307 and the medial annular flange 310. The spacer/stopper113 interfaces with the flat face 387 of the distal fitting 374 of theintermediate connection mount 109 when pushed upon by the medial annularflange 310 to arrest proximal travel of the helical anchor electrode108. The spacer/stopper 113 also interfaces with the sleeve shoulder 329between the sleeve bore 328 and the narrower diameter middle bore 332 ofthe tip housing 110 when pushed by the proximal annular flange 307 toarrest distal travel of the helical anchor electrode 108.

The seal ring 115 is stretched over the distal annular flange 312 toreside on the seal shaft section 306 between the medial and distalannular flanges 310, 312. The seal ring 115 is positioned within themiddle bore 332 of the tip housing 110 and is configured to interfacewith the inner wall defining the middle bore 332 to provide afluid-tight seal. The inner diameter of the cylindrical section 391 isdesigned to fit against the seal shaft section 306. The radius entrance398 to the center aperture 396 from the distal side of the seal ring 115helps reinforce the seal with respect to the seal shaft section 306 onthe tip electrode pin 105 as well as provide for easy release of thecore molding pin during manufacturing. The angled design of the radialwall 393 on the outer diameter also helps reinforce the seal against themiddle bore 332. The seal ring 115 remains within and travels along alength of the middle bore 332 for all positions of the helical anchorelectrode 108 and as it is advanced or retracted, thereby maintainingthe fluid-tight seal at all times while also providing for a lowfriction force on the middle bore 332.

The marker band 111 may be molded separately and then insert molded intothe tip bore 338 during the molding process for the tip housing 110. Twoopposing ones of the four sidewall retention holes 322 are positioned toallow molding material of the tip housing 110 to flow into and aroundthe marker band 111, thus providing a form for the retention posts 331,the outer diameter of the guide walls 334, the diameter for the tip bore338 and the shelf shoulder 335 of the tip housing 110. The marker band111 is thereby held in place within the tip bore 338 by the retentionposts 331. The other two sidewall retention holes 322 remain clearduring the insert molding process, are aligned with the retentionapertures 330 formed in the tip housing 110, and are provided foraccepting the two retention plugs 348 a/b of the soft tip plug 117.

The soft tip plug 117 also fits within the tip bore 338 such that thearcuate walls 346 a/b fit between the guide walls 334 in the tip bore338 of the tip housing 110. The retention plugs 348 a/b fit within theretention holes 322 of the marker band 111 and the retention apertures330 of the tip housing 111 to retain the soft tip plug 117 on the distalend of the tip housing 110. The complicated geometry of the bond betweenthe soft tip plug 117 and the tip housing 110 is configured to besufficiently strong to carry any mechanical loads during implantationand ensure long term life in the heart. In some implementations, thesoft tip plug 117 may receive a steroid capsule (e.g., dexamethasone) orother medicament.

The sleeve bore 328 of the tip housing 110 fits over and bonds to thedistal fitting 374 of the intermediate connection mount 109. The tiphousing 110 may be bonded to the distal fitting 374 with a friction fit,medical adhesive, or both to ensure that the tip housing 110 ispermanently affixed to the lead 100. The tip housing 110 provides ahousing for the helical anchor electrode 108 in the retracted positionduring lead insertion in the patient. Once the distal end 104 of thelead is in place, the tip housing 110 provides several features centralto the functionality of the implantation of the helical anchor electrode108 into myocardial tissue. As shown in FIGS. 10B and 10C, the anchorguide 336 in the tip housing 110 is positioned between adjacent windingsof the helical anchor electrode 108. In order to extend or advance thehelical anchor electrode 108 beyond the soft tip plug 117, the physicianrotates the connector pin 112 at the proximal end 102 of the lead 100clockwise. The rotational motion of the connector pin 112 is translatedalong the length of the inner conductor coil 120 to the tip electrodepin 105, which further translates the rotation to the helical anchorelectrode 108. Because the anchor guide 336 is positioned between thewindings of the helical anchor electrode 108, the helical anchorelectrode 108 is advanced distally as it rotates rather than merelyrotating in a constant longitudinal position.

As the connector pin 112 is rotated by the physician, the tip electrodepin 105 advances distally within the intermediate connection mount 109and the tip housing 110 as the helical anchor electrode 108 interfacingwith the anchor guide 336 functions as a worm drive. The medial shaftsection 304 of the tip electrode pin 105 slides through the cylindricalaperture 391 of the spacer/stopper 113 until the proximal annular flange307 reaches the spacer/stopper 113 and begins to push it distally. Thetip electrode pin 105, and thus the helical anchor electrode 108 areable to advance distally because the inner conductor coil 120 is a coiland can thus expand slightly along its length as the helical anchorelectrode 108 advances with respect to the anchor guide 336, whichremains in a stationary position within the tip housing 110. Theextension of the helical anchor electrode 108 is arrested when thespacer/stopper 113 interfaces with the sleeve shoulder 329 of the tipsleeve 110 as shown in FIG. 10C and blocks further distal advancement ofthe proximal annular flange 307 of the tip electrode pin 105. At thispoint, the helical anchor electrode 108 should be sufficiently embeddedwithin the endocardial tissue to hold the active electrode tip 106permanently in place without completely perforating the wall of theheart.

If the helical anchor electrode 108 needs to be retracted, e.g., forrepositioning or removal of the lead 100, the physician can rotate theconnector pin 112 counterclockwise at the proximal end 102 of the lead100. This counterclockwise movement is translated along the length ofthe inner conductor coil 120 to the tip electrode pin 105, which furthertranslates the rotation to the helical anchor electrode 108. Because theanchor guide 336 is positioned between the windings of the helicalanchor electrode 108, the helical anchor electrode 108 acts as a wormdrive and is retracted proximally as it rotates rather than merelyrotating in a constant longitudinal position. The retraction of thehelical anchor electrode 108 is arrested when the spacer/stopper 113interfaces with the distal fitting 374 of the intermediate connectionmount 109 and blocks further proximal movement of the medial annularflange 310 of the tip electrode pin 105. At this point, the helicalanchor electrode 108 should be fully retracted and housed within the tiphousing 110 and no further retraction is necessary. In this way, thewindings of the helical anchor electrode 108 remain engaged with theanchor guide 336. If the helical anchor electrode 108 were to beretracted too far such that there was no longer an interface with theanchor guide 336, the helical anchor electrode 108 could not be advancedor retracted and would merely rotate in the same longitudinal position.

With reference to FIGS. 21, 22A, 22B, 22C, 23A, and 23B, an alternativeproximal end of the lead of FIG. 1 is provided with a snap-fitconnection between the connector insulator 716 and the ring connector730. The connector insulator 716 and the ring connector 730 are designedto snap together to axially secure the parts together. The snapengagement may improve the mechanical strength of the connection jointbetween the components. Additionally or alternatively, the snapengagement may eliminate the use of medical adhesive or otherbio-compatible glue for connecting the connector insulator 716 and thering connector 730. Optionally, in some implementations, medicaladhesive may be used to further enhance the joint strength and seal anair gap between the connector insulator 716 and the ring connector 730.

As shown in FIGS. 22A through 22C, the connector insulator 716 includessimilar features as the connector insulator 116 shown in FIGS. 5A and 5Bexcept the connector insulator 716 includes at least one tab 705extending radially outward from the inner shoulder surface 727, whichmay form part of the distal extension 786. In the exemplary embodimentshown, the connector insulator 716 includes three tabs 705 evenly spacedabout the periphery of the inner shoulder surface 727. The tabs 705 arepositioned about a distal portion of the inner shoulder surface 727,thereby defining an annular recess 707 located proximally of the tabs705. The tabs 705 each include a chamfered distal surface 709, asubstantially square proximal shoulder 713, and a curved surface 711located intermediate the chamfered surface 709 and the square shoulder713. The curved surfaces 711 of the three tabs 705 follow the curve of acylinder axially aligned with a center longitudinal axis of theconnector insulator 716. The interface between the chamfered surface 709and the curved surface 711 may be arcuate, curved, or rounded. Theannular recess 707 is defined by the inner shoulder surface 727, whichserves as a base wall for the recess 707. The inner shoulder surface orbase wall 727 of the recess 707 is positioned between the squareproximal shoulder 713 and an opposing, radially-extending sidewall 732.The outer diameter of the tabs 705 is greater than the inner diameter ofannular recess 707 and may be less than the diameter of the outersurface 729 of the central body 782.

As shown in FIGS. 23A and 23B, the ring connector 730 includes similarfeatures as the ring connector 130 shown in FIGS. 7A and 7B except theproximal end of the ring connector 730 includes an annular groove 821.The annular groove 821 is positioned axially between a proximalretaining shoulder 823 and a distal limit shoulder 825. The proximalretaining shoulder 823 may be substantially perpendicular relative to agroove wall 827, and the distal limit shoulder 825 may be angled orramped relative to the groove wall 827. Thus, the distal limit shoulder825 may be angled relative to the proximal retaining shoulder 823. Thegroove 821 is configured to receive the at least one tab 805 of theconnector insulator 716.

The proximal end of the ring connector 730 also includes a radiallyinturned lip 831 located proximally of the groove 821. The radiallyinturned lip 831 has an inner cylindrical surface 862 locatedintermediate the retaining shoulder 823 and the proximal flat face 860.The interface 864 between the inner cylindrical surface 862 and the flatface 860 may be chamfered. The cylindrical surface 862 has an innerdiameter that is less than the diameter of the substantially flat groovewall 827 and may be substantially equal to the diameter of the innerwall 861 of the band portion 804.

With continued reference to FIGS. 21, 22A, 22B, 22C, 23A, and 23B, theinturned, proximal lip 831 of the ring connector 730 is configured toseat in the recess 707 of the connector insulator 716, and the tabs 705of the connector insulator 716 are configured to seat in the groove 821of the ring connector 730. The width of the lip 831 may be congruentwith the width of the annular recess 707 to substantially prevent axialdisplacement of the lip 831 within the recess 707. In thisconfiguration, the proximal face 860 of the ring connector 103 may abutthe step surface 732 of the central body 782 of the connector insulator716 and the distal retaining shoulder 823 of the inturned lip 821 mayabut the square proximal shoulder 713 of the tabs 705 to axiallyinterlock the ring connector 730 and the connector insulator 716. Theheight of the lip 831 may be congruent with a depth of the annularrecess 707 to maintain a flush transition between the outer surfaces ofthe ring connector 730 and the connector insulator 716. That is, thedistance between the inner cylindrical surface 862 of the inturned lip831 and the outer surface of the band portion 804 of ring connector 730may be approximately equal to the distance between the inner shouldersurface 727 of the annular recess 707 and the outer surface 729 of thecentral body 782 of the connector insulator 716.

During connection of the ring connector 730 and the connector insulator716, the chamfered interface 864 between the face 860 and thecylindrical surface 862 of the ring connector 730 contacts the chamfereddistal surface 709 of the tabs 705 of the connector insulator 716.Depending upon the material properties of the ring connector 730 and theconnector insulator 716, the lip 831, the tabs 705, or both mayresiliently deform to permit the lip 831 to pass axially by the tabs705. Once the lip 831 clears the tabs 705, the lip 831, the tabs 705, orboth elastically return to their non-deformed states to axiallyinterconnect the ring connector 730 and the connector insulator 716. Insome implementations, the lip 831 may frictionally engage at least onesurface of the annular recess 707, the tabs 705 may mechanically engageat least one surface of the groove 821, or both, to constrict rotationof the ring connector 730 relative to the connector insulator 716. Insome implementations, the ring connector 730 and the connector insulator716 may be disconnected from each other without permanently damagingeither component.

The mechanical strength of the snap or interference fit between the ringelectrode 730 and the connector insulator 716 depends upon the design ofthe locking feature of the components. For example, the materialstrength, elasticity, diameter, and thickness of the locking features(i.e., the lip 831 and the tabs 705) affect the mechanical snap-fitconnection strength. The tabs 705 of the connector insulator 716 shownin the exemplary embodiment of FIGS. 22A through 22C extenddiscontinuously around the periphery of the mount 109. That is, theconnector insulator 716 includes three discrete tabs 705 spaced about aperiphery of the connector insulator 716. The tabs 705 extend about aminority of the periphery of the insulator 716. The outer side surfaces753 of the tabs 705 may extend approximately perpendicular to the innershoulder surface 727. The tabs 705 also include a chamfered distalsurface 709 to reduce an insertion force and a square proximal shoulder713 to increase a disconnection force. The lip 831 of the ring connector730 extends continuously around the inner periphery of the connector730. The lip 831 also includes a chamfered proximal surface 864 forreducing an insertion force and a square distal surface 823 to matinglyengage the squared shoulder 713 of the connector insulator 716 andincrease a disconnection force. In an alternative implementation, theconnector insulator 716 may include a single, continuous tab 705extending in a ring about the periphery of the insulator 716 to increasethe strength of the snap engagement connection by increasing the amountof material engagement between the ring connector 730 and the connectorinsulator 716.

With reference to FIGS. 22D through 22F, an alternative connectorinsulator 916 is provided. The insulator 916 generally has the samefeatures as the connector insulator 716 depicted in FIGS. 22A through22C except the tabs 905 are modified to reduce the cost and complexityof manufacturing the snap lock feature associated with the connectorinsulator 916. The connector insulator 916 includes a plurality of tabs905 unevenly distributed about the periphery of the inner shouldersurface 927. The tabs 905 are symmetric with respect to thecross-sectional plane defining the cross section depicted in FIG. 22Eand include an upper tab 905A and two lower tabs 905B, 905C. The lowertabs 905B, 905C each include an outer side surface 953 that issubstantially tangential to the outer circumference of the innershoulder surface 927 and which are substantially parallel to each other.The substantially tangential and substantially parallel configuration ofthe side surfaces 953 may reduce the cost and complexity ofmanufacturing the lower tabs 905B, 905C without sacrificing mechanicalstrength of the snap-fit joint between the connector insulator 916 andthe ring connector 730.

In some implementations, a multi-piece mold is used to form the tabs905. The substantially tangential configuration of the side surfaces 953of the lower tabs 905B, 905C may enable the use of a two-piece, orhalf-shell, mold. Each half of the mold can be radially removed from theconnector insulator 916 after formation of the tabs 905 in opposingdirections parallel to the outer side surfaces 953 of the lower tabs905B, 905C with relative ease. If the side surfaces 853 were formed at alesser angle than tangential to the base wall 815 and not parallel toeach other, release of the two-piece, or half-shell, mold from the tabs905 may be difficult, which may result in damage to the connectorinsulator 916 and/or the mold. Thus, in some implementations, e.g., inthe embodiment of FIGS. 22A-22C, a three-piece or a higher number moldmay be used during manufacturing if the tabs 905 are not formed with thesubstantially tangential and parallel side surfaces 953. The three-pieceor higher number mold may reduce damage to the parts, with the drawbackof additional manufacturing pieces. Although only two oblique sidesurfaces 953 are shown in FIGS. 22D through 22F, the tabs 905 mayinclude any number of oblique side surfaces 953.

With reference to FIGS. 22G through 22I, another alternative connectorinsulator 1016 is provided. The connector insulator 1016 generally hasthe same features as the connector insulator 716 depicted in FIGS. 22Aand 22C except the snap interlock feature includes only two tabs 1005.The tabs 1005 depicted in FIGS. 22G through 22I each have substantiallythe same cross-sectional shape as the tab 705 depicted in FIGS. 22Athrough 22C. That is, the tabs 1005 each have a chamfered distal surface1009 (although the slope of the chamfered distal surface 1009 is longerthan the chamfered surface 709 of the tab 705), a substantially squaredistal shoulder 1013, and a curved surface 1011 located intermediate thechamfered surface 1009 and the square shoulder 1013. The curved surfaces1011 of each of the tabs 1005 follow the curve of a cylinder axiallyaligned with a center longitudinal axis of the connector insulator 1016.However, in contrast to the three tab 705 configuration of FIGS. 22Athrough 22C, in FIGS. 22G through 22I two discontinuous tabs 1005 aredisposed around the periphery of the inner shoulder surface 1027. Inparticular, two diametrically opposed tabs 1005 protrude outwardly fromthe shoulder surface 1027 of the connector insulator 1016. The tabs 1005collectively extend around a minority of the periphery of the shouldersurface 1027, although in other implementations the tabs 1005 may extendaround one-half or a majority of the periphery of the shoulder surface1027. Since the tabs 1005 are discontinuous and spaced apart from eachother, voids are formed between the tabs 1005. The voids reduce theamount of material that engages the lip 831 of the ring connector 730,thereby reducing the mechanical strength of the snap-fit connectionrelative to a snap lock feature including a tab extending continuouslyaround the periphery of the shoulder surface 1027.

The locking feature of the connector insulator 716, 916, 1016 mayinclude any number of tabs. Generally, the inner shoulder surface of theconnector insulator includes at least one tab, which may extendcontinuously or discontinuously around the periphery of the connectorinsulator. The at least one tab may extend around a minority, one-half,or a majority of the circumference of the inner shoulder surface of theconnector insulator. The at least one tab may have a suitablecross-sectional shape to provide a suitable interlock insertion andretention force. The at least one tab may include a substantially squareproximal shoulder to increase the mechanical strength of the mechanicalsnap-fit joint between the connector insulator and the ring connector.At least one side surface of the at least one tab may extend at anoblique angle, including tangential, from a circumferential surface ofthe connector insulator to reduce the cost and/or complexity ofmanufacturing the locking feature of the connector insulator, aspreviously discussed. Additionally or alternatively, at least one sidesurface of the at least one tab may extend perpendicular relative to theinner shoulder surface of the connector insulator.

With reference to FIG. 24, an isometric view of an embodiment of animplantable medical passive electrical lead 400 is provided. The lead400 has a proximal end 402 and a distal end 404. As shown, a passive tip406 may be disposed at the distal end 404 and may include a passive tipsheath 408 in the form of an anchor-type fixation mechanism. The passivetip sheath 408 may be designed to anchor the lead at a treatment site ofa patient such as in the fibrous tissue lining the endocardium of aheart, for example. The passive tip sheath 408 may include one or moreradially spaced tines 410 that engage the treatment site or othertissues adjacent to the treatment site thereby holding the distal end ator near the treatment site. As shown in FIG. 24, the lead 400 islongitudinally extended between the distal end 404 and the proximal end402.

Referring now to FIG. 25, the proximal end 402 of the lead 400 includesa system of parts or pieces. The system of parts or pieces may bedivided into three categories including inner parts relating to an innerconductor, outer parts relating to an outer conductor, and insulatingparts for electrically separating the inner parts from the outer parts.The inner parts may include a conductive connector pin 412, an innerconductor or coil 420, and a pin sleeve 422. The outer parts may includea ring connector 430, an outer conductor or coil 434, and a ring sleeve436. The inner and outer parts may be substantially separated by theinsulating parts including a connector insulator 416 and an insulatortubing 424. A proximal seal 414 and a boot seal 440 may also beprovided.

As shown in FIG. 25, the design of the proximal end 402 of the lead 400is similar to the design of the proximal end 102 of the lead 100, exceptthat the proximal seal 414 and the connector insulator 416 are slightlymodified as compared to the proximal seal 114 and the connectorinsulator 116. The conductive connector pin 412, the inner conductor orcoil 420, and the pin sleeve 422 are the same as the conductor connectorpin 112, the inner conductor or coil 120, and the pin sleeve 122,respectively, previously discussed in connection with the lead 100.Thus, the description of these parts is not repeated here.

As shown in FIGS. 25 through 26B, the connector insulator 416 is similarto the connector insulator 116 in many respects. For example, thecentral body 482 and the distal extension 486 are substantially the sameas the central body 182 and the distal extension 186. However, theproximal extension 484 only extends partially through a center bore 450of the proximal seal 414, in contrast to the proximal extension 184,which extends fully through a center bore 150 of the proximal seal 114.

A close-up view of the connector insulator 416 is shown in FIGS. 26A and26B. The connector insulator 416 may be configured for sleevablyisolating the connector pin 412 and a portion of the inner conductor 420from the outer parts. In addition, the connector insulator 416 may beconfigured for supporting a portion of the proximal seal 414. Theconnector insulator 416 may include a central body 482, a proximalextension 484, and a distal extension 486. The central body 482 mayinclude a substantially cylindrically shaped body having an outerdiameter. The distal extension 486 may also be substantiallycylindrically shaped and may include an outer diameter smaller than thatof the central body 482.

The proximal extension 484 of the connector insulator 416 may extendfrom the proximal end of the central body 482 and may be substantiallycylindrical with a diameter smaller than that of the central body 482.The transition between the central body 482 and the proximal extension484 may define a proximal shoulder 483 opposite the cascading shouldersdescribed. The interface between the proximal extension 484 and theproximal shoulder 483 may be formed as a small, concave, annular radius485. The proximal extension 184 may extend partially underneath theproximal seal 414. As such, when the proximal seal 414 is positioned onthe proximal extension 484 a distal end of the proximal seal 414 mayabut the proximal shoulder 483 of the central body 482 and the proximalend of the connector insulator 416 may align with a shoulder 497 withina center bore 450 of the proximal seal 414 as shown in FIGS. 25 and 27B.

The connector insulator 416 may include center bore 418 with a diameterconfigured for receiving the bar portion 464 of the connector pin 412.The center bore 418 may extend from the proximal end of the insulator416 to a point within the central body 482 of the insulator 416 wherethe center bore 418 may transition to a bore 419 with a larger diameter.The bore 419 with the larger diameter may accommodate the increaseddiameter of the conductor end 462 of the connector pin 412. The diameterof the bores 418, 419 may closely fit the respective portions of theconnector pin 412. The bore 419, with its larger diameter, may extendthrough the remaining portion of the central body 482 and through thedistal extension 486 of the connector insulator 416.

The connector insulator 416 may be constructed from a bio-compatiblegrade of insulator material. This material may be selected to providesufficient mechanical strength, elasticity, and insulationcharacteristics. For example, as described with respect to the connectorpin 412, the conductor end 462 of the connector pin 412 may be pressedthrough the bore 418 of the connector insulator 416. As such, theconnector insulator 416 may be made of a relatively strong yet elasticmaterial allowing the pin 412 to be driven therethrough without loss ofstrength and without permanent deformation. In some embodiments, theconnector insulator 416 may be made from a moldable thermoplastic suchas polyurethane, polysulfone, or PEEK. Still other material may beselected to provide the suitable strength, elasticity, and insulationcharacteristics.

While elastic, the connector insulator 416 may also be designed tosecure the connector pin 412 and prevent the connector pin 412 frombeing removed or withdrawn from the proximal end of the lead 400. Aproximal shoulder 431 at the proximal end of the conductor end 462 ofthe connector pin 412 may be provided to transition to the smallerdiameter bar portion 464. A surface 435 of the shoulder 431 may interactwith an opposing surface 437 of shoulder 433 on the interior surface ofthe connector insulator 416. The shoulder 433 on the interior of theconnector insulator 416 may be formed as the transition between the bore418 and bore 419. The relative diameters of the bar portion 464 and bore418 and the relative diameters of the conductor end 462 and bore 419 maybe selected to allow the connector pin 412 to rotate within theconnector insulator 416. However, to prevent removal therefrom, thediameter of the conductor end 462 may be selected to be larger than thediameter of the bore 418. In addition, the material of connectorinsulator 416 may be selected to be rigid enough to prevent withdrawalof the connector pin 412 under withdrawal loads or strengths specifiedby the IS-1 specification, for example.

The proximal seal 414 may be configured for secured placement on theconnector insulator 416 and for sealingly engaging a socket on anelectrical stimulation device. In addition, the proximal seal 414 mayfunction, together with the connector insulator 416, to electricallyisolate and prevent crosstalk between the ring connector 430 and theconnector pin 412. As shown in FIGS. 27A and 27B, the proximal seal 414may include a flush portion 498 and a seal portion 499. The flushportion 498 may be distal to the seal portion 499 and may function toencompass the proximal extension 484 of the connector insulator 416 andabut the central body 482 thereof. The flush portion 498 may besubstantially cylindrical with an outer diameter substantially matchingthe outer diameter of the central body 482 of the connector insulator416 thereby being flush therewith. The seal portion 499 may be proximalto the flush portion 498 and may also be substantially cylindrical withan outer diameter slightly larger than the flush portion 498. The sealportion 499 may include one or more (e.g., two) annular,radially-extending ribs 496 protruding from the outer surface of theseal portion 499 and defining relatively deep channels 495 in between.The ribs 496 may extend from the seal portion 499 such that the outersurface or tip of the ribs 496 defines a diameter larger than the flushportion 498. The diameter of the channels 495 may be smaller than thediameter of the flush portion 498 such that there is a stepped shoulder495 between a base wall 493 of the channel 495 and the flush portion498. A proximal annular lip 491 of the proximal seal 414 may have asimilar diameter to the diameter of the channels 495 at the base wall493 and may extend proximally as an annular ring from the most proximalrib 496. The ribs 496 may be adapted to engage a cylindrical socket andmay have an outer diameter at least slightly larger than the diameter ofthe socket so as to sealingly engage an inner surface of the socket andprevent fluids or other matter from traveling into the socket andreaching the connector pin 412 or otherwise leaking into the electricalstimulation device.

The proximal seal 414 may include a bore 450 extending from the proximalend that expands to form a larger diameter distal bore 451 at the distalend. The smaller diameter bore 450 may be sized to seal against theouter diameter of the bar portion 464 of the connector pin 412. The barportion 464 may further be fixed to an inner surface 456 of the bore 450by a medical adhesive or other bio-adaptable adhesive equivalent. Asquared shoulder 497 may be formed by the step in diameter between thebore 450 and the distal bore 451.

The diameter of the distal bore 451 may be substantially equal to theouter diameter of the proximal extension 484 of the connector insulator416. When inserted within the distal bore 451, the proximal extension484 may abut and seal against the squared shoulder 497. In someembodiments, the proximal seal 414 may be made of a resilient materialand the diameter of the distal bore 451 may be slightly smaller than theouter diameter of the proximal extension 484 of the connector insulator416 such that the proximal seal may be stretched to receive theconnector insulator 416 thereby compressively receiving the connectorinsulator 416 therein. The proximal seal 414 may be made from a suitablyresilient material to compressively seal the proximal end 402 of thelead 400 with the electrical stimulation device. In some embodiments,the seal 414 may be a biocompatible silicone, for example. Still othermaterials may be selected to suitably seal the proximal end 402 of thelead 400 with the electrical stimulation device and also be compatiblewith the body.

Having described the inner parts and the isolation thereof by theinsulator tubing 424 and the connector insulator 416, the outer partsmay now be described. As shown in FIG. 25, the outer parts may includethe ring connector 430, an outer conductor or coil 434, and a ringsleeve 436. The ring connector 430, the outer coil 434, and the ringsleeve 436 are the same as the ring connector 130, the outer coil 134,and the ring sleeve 136, respectively, previously discussed inconnection with the lead 100. Thus, the description of these parts isnot repeated here. Similarly, the ring sleeve 336 and the boot seal 340are the same as the ring sleeve 136 and the boot seal 340 previouslydiscussed in connection with the lead 100, and thus the description ofthese parts is not repeated here.

Referring again to FIG. 25, the assembled proximal end of the lead maybe described. As shown, the electrically conductive connector pin 412may extend through and may be disposed in a center bore 450 of aproximal seal 414 and a center bore 418 of a connector insulator 416.The bar portion 464 of the connector pin 412 may be arranged in thecenter bore 418. A distal part of bar portion 464 may be separated fromthe inner surface of the center bore 450 by the proximal extension 484of the connector insulator 416. The electrically conductive innerconductor or coil 420 may be crimped to the conductor end 462 of theconnector pin 412 in conjunction with the pin sleeve 422. The innerinsulator tubing 424 may extend over the inner coil conductor 420 andthe flared portion 426 thereof may be sleeved onto the distal extension486 of the connector insulator 416 to create a fluid-tight, compressionfit therewith. The inner insulator tubing 424 may abut the innershoulder 490 of the cascading shoulders and having an outer surfacesubstantially flush with the cylindrical outer surface 427 of the innershoulder 490. As such, the connector pin 412, the crimp connection, andthe inner coil 420 may be substantially fully insulated along its lengthby the connector insulator 416 and the insulator tubing 424. However,the inner conductor 420 may be exposed via an electrode at the distalend 404 for treatment and the connector pin 412 may be exposed at theproximal end 402 for electrical communication with an electricalstimulation device. The proximal seal 414 may be arranged on theconnector insulator 416 and the outwardly projecting ribs 496 may engagea socket on an electrical stimulation device to prevent fluid or otherliquid from contacting with the connector pin 412.

The band portion of the ring connector 430 may extend over the flaredportion 426 of the insulator tubing 424 and may abut the outer shoulder488 of the cascading shoulders on the connector insulator 416. As shown,the outer surface of the band portion of the ring connector 430 may beflush with the outer surface 429 of the central body 482 of theconnector insulator 416. The outer conductor or outer coil 434 may bearranged to receive the inner coil 420 and insulator tubing 424concentrically within the outer conductor or coil 434. The outerconductor or coil 434 may be crimped to the ring connector 430 by a ringsleeve 436, thereby electrically connecting to the ring connector 430.The boot seal 440 may be positioned over the outer coil 434 and aninwardly protruding rib 443 thereof may engage a slot portion of thering connector thereby securing the position of the boot seal 440relative to the ring connector 430. The crimped outer coil 434 andportions of the ring connector 430 may be disposed within a center bore441 of the boot seal 440. Like the proximal seal 414, the radiallyprojecting ribs 444 of the boot seal 440 may engage a socket on anelectrical stimulation device to prevent body fluid or other liquid fromcontacting the ring connector 430 or otherwise entering the electricalstimulation device.

Accordingly, the connector pin 412 may be electrically connected to theinner coil 420, and the ring connector 430 may be electrically connectedto the outer coil 434. In operation of the lead, electrical signals maybe sent from the proximal end 402 to the distal end 404 via theconnector pin 412 and the inner coil 420, and via the ring connector 430and the outer coil 434. The inner coil 420 may be electrically insulatedfrom the outer coil 434 by the inner insulator tubing 424. The ringconnector 430 may be electrically insulated from the inner coil 420 bythe inner insulator tubing 424 and the connector insulator 416. Theconnector pin 412 may be electrically insulated from the ring connector430 by the proximal seal 414 and the connector insulator 416. Theconnector pin 412 may be prevented from contacting fluid or other liquidby the sealing ribs 496 of the proximal seal 414. The ring connector 430may be prevented from being in contact with fluid or other liquid by thesealing ribs 444 of the boot seal 440.

The passive tip 408 at the distal end 404 of the lead 400 is depicted incross section in FIG. 28. The passive tip 406 may be considered to becomposed primarily of a ring electrode 403, a tip electrode 405, and apassive tip sheath 408. A proximal end of the ring electrode 403 iselectrically and mechanically connected to the distal end of the outerconductor coil 434. The proximal end of the tip electrode 405 iselectrically and mechanically connected to the distal end of the innerconductor coil 420. The distal end of the ring electrode is connected tothe proximal end of the passive tip sheath 408. The proximal portion ofthe tip electrode is substantially encased within the passive tip sheath408 with the exception of an annular tip face 508 that is exposed andabuts a distal end of the passive tip sheath 408.

The tip electrode 405 is depicted in greater detail in FIGS. 29A and29B. The tip electrode may be generally cylindrical in shape with anumber of stepped outer diameters, beginning at the proximal end with aproximal shaft section 502 of the smallest diameter. The proximal shaftsection 502 is the section of the tip electrode 405 that engages theinner conductor coil 420 as will be described in further detail below.The proximal shaft section 502 transitions into a larger diameter medialshaft section 504 at a medial shoulder 503. The medial shaft section 504may further transition distally into an even larger outer diameterbarrel section 506 at a barrel shoulder 505, which is the section of thetip electrode 405 that may interface with an annular shelf 537 of thepassive tip sheath 408 (see FIG. 30B) to help retain the passive tipsheath 408 on the lead 400. The barrel section 506 may furthertransition to the annular tip face 508 having and even larger outerdiameter at a tip shoulder 509. The annular tip face 508 may be exposedto the patient's blood and tissue when the lead 400 is implanted invivo. The electrode tip 405 may thus be made of a precious metal, forexample, Pt/Ir, Pt, or another electrically conductive, biocompatiblematerial. The tip shoulder 509 may further interface with an annularface 525 of the passive tip sheath 408 (see FIGS. 30A and 30B) toadditionally help retain the passive tip sheath 408 on the lead 400.

The outer surface of the tip face 508 may be formed as a radiused curvefrom the tip shoulder 509 to a point at which an entrance to a steroidcavity 510 within the barrel section 506 is defined. The steroid cavity510 may be generally cylindrical as it extends within the barrel section506. In the exemplary embodiment shown in FIG. 29B, the base wall 514 ofthe steroid cavity 510 may be formed as a concave conical surface. Thesidewalls of the barrel section 506 may define one or more (in thisexample, two) adhesive apertures 512 for introduction or release ofadhesive through the steroid cavity 510 onto the outer surface of thebarrel portion 506 to create an adhesive bond with the passive tipsheath 408. Adhesive may also be provide in the concave are formed inthe based wall 514 in the steroid cavity 510 in order to assist inretaining the steroid 407 therein.

One exemplary embodiment of a passive tip sheath 408 is depicted ingreater detail in FIGS. 30A and 30B. The passive tip sheath 408 may begenerally cylindrical in shape with a long tubular sheath 520 formingthe proximal section thereof. The tubular sheath 520 may transition at astepped shoulder 521 to a narrower diameter tine recess section 522.Immediately distal to the tine recess section 522 is a tine section 523from which a plurality of tines 410 (in this exemplary embodiment, four)protrude at a number of evenly-spaced circumferential locations aboutthe tine section 523. The tines 410 extend proximally from the tinesection 523 at an acute angle with respect to the recess section 523.The passive tip sheath 408 may extend a short length further distallyfrom the tine section 523 in a sloped section 524 that tapers indiameter until terminating at an annular face 525.

The tines 410 may be integrally formed with the passive tip sheath 408and may flex at the interface with the tine section 523 in the manner ofa living hinge. The tines 410 may flex radially inward and fold flatagainst the recess section 522 such that the outer diameter across therecess section 522 when the tines 410 are folded down is substantiallythe same as the outer diameter of the tubular sheath 520. In thismanner, when the lead 400 is advanced through a catheter for in vivoplacement, the tines 410 can fold against the recess section 522 and thepassive electrode tip 406 can easily pass through a delivery catheter.When the passive electrode tip 406 emerges from the distal end of thedelivery catheter, the tines will spring radially outward and provideanchor structures to anchor the distal end 404 of the lead 400 incardiac tissue. The passive tip sheath 408 may be formed of a resilientbiocompatible elastomeric material in order to both provide for theresilient properties needed for the tines 410 and to be fitted over thetip electrode 405 and other structures and retained thereon.

The passive tip sheath 408 may define a lumen 526 therethrough in orderto be fitted over the tip electrode 405, a length of the inner coil 420,and the distal end of the ring electrode 403 as will be furtherdescribed herein in greater detail. At a proximal end, the lumen maydefine a sleeve bore 528 of relatively large diameter with respect tothe rest of the lumen 526 that is sized in both diameter and length tosleeve over and create a fluid-tight connection with the connectionsection 560 of the ring electrode 403. The sleeve bore 528 transitionsat a sleeve shoulder 529 to a relatively long inner coil bore 530 of anarrower inner diameter that is sized to extend over the inner conductorcoil 420 for a length until the inner conductor coil 420 couples withthe tip electrode 405. The inner coil bore 530 transitions to a middlebore 532 of larger inner diameter along a sloped section 531 thatgradually increases the inner diameter between the two bore sections.The middle bore 532 is sized in diameter and length to fit about aconnection between the connection between the outer insulating tubing424 and the proximal end of the tip sleeve 409.

The middle bore 532 transitions to a tip sleeve bore 534 of smallerdiameter at a squared shoulder 533 that abuts a distal end of the innerinsulating tubing 424. The tip sleeve bore 534 covers the remainder ofthe tip sleeve 409 that forms a crimp connection with the tip electrode405. The tip sleeve bore 534 then transitions to a tine bore 536, whichis generally coextensive with the tine section 523 on the outer surfaceof the passive tip sheath 408 and which houses the medial shaft section504 of the tip electrode 405. Finally, the lumen 526 exits the distalend of the passive tip sheath 408 through a tip bore 538 that is of alarger diameter than the tine bore 536 and which is sized to house thebarrel section 506 of the tip electrode 405. The annular shelf 537 actsas a shoulder at the change in diameter between the tine bore 536 andthe tip bore 538. The annular shelf 537 acts as an axial stop abuttingthe tip shoulder 509 of the tip electrode 405 to prevent the passive tipsheath 408 from sliding distally off of the lead 400.

Another exemplary embodiment of a passive tip sheath 608 is depicted ingreater detail in FIGS. 30C and 30D. It is in many respects similar tothe passive tip sheath 408 of FIGS. 30A and 30B except for the proximalend. For example, the passive tip sheath 608 may be generallycylindrical in shape with a long tubular sheath 620 forming a primarysection thereof. At a proximal end, tubular sheath 620 transitions at asheath shoulder 629 to define a proximal insert 628 of a smallerdiameter than the tubular sheath 620 that is sized in both diameter andlength to be inserted within and create a fluid-tight connection withthe distal end of an alternate embodiment of the ring electrode 603 asfurther described below. The proximal insert 628 may be formed ofalternating sections of recessed wall 616 and protruding wall 618oriented longitudinally with respect to length of the passive tip sheath608. The protruding wall section 618 creates a tight, friction fit withthe ring electrode 603 and the recessed wall sections 616 provideadhesive wells for receiving biocompatible adhesive to permanentlyconnect the passive tip sheath 608 to the ring electrode 603 as furtherdescribed below.

Toward the distal end, the tubular sheath 620 may transition at astepped shoulder 621 to a narrower diameter tine recess section 622.Immediately distal to the tine recess section 622 is a tine section 623from which a plurality of tines 610 protrude at a number ofevenly-spaced circumferential locations about the tine section 623. Thepassive tip sheath 608 may extend a short length further distally fromthe tine section 623 in a sloped section 624 that tapers in diameteruntil terminating at an annular face 625.

The passive tip sheath 608 may define a lumen 626. A relatively longinner coil bore 630 of a constant inner diameter that is sized to extendover the inner conductor coil 420 extends from the proximal insert 628for a length until the inner conductor coil 420 couples with the tipelectrode 405. The inner coil bore 630 transitions to a middle bore 632of larger inner diameter along a sloped section 631 that graduallyincreases the inner diameter between the two bore sections. The middlebore 632 is sized in diameter and length to fit about a connectionbetween the connection between the outer insulating tubing 424 and theproximal end of the tip sleeve 409.

The middle bore 632 transitions to a tip sleeve bore 634 of smallerdiameter at a squared shoulder 633 that abuts a distal end of the outerinsulating tubing 424. The tip sleeve bore 634 covers the remainder ofthe tip sleeve 409 that forms a crimp connection with the tip electrode405. The tip sleeve bore 634 then transitions to a tine bore 636, whichis generally coextensive with the tine section 623 on the outer surfaceof the passive tip sheath 608 and which houses the medial shaft section504 of the tip electrode 405. Finally, the lumen 626 exits the distalend of the passive tip sheath 608 through a tip bore 638 that is of alarger diameter than the tine bore 636 and which is sized to house thebarrel section 306 of the tip electrode 405. The annular shelf 637 actsas a shoulder at the change in diameter between the tine bore 636 andthe tip bore 638. The annular shelf 637 acts as an axial stop abuttingthe tip shoulder 309 of the tip electrode 405 to prevent the passive tipsheath 608 from sliding distally off of the lead 400.

FIG. 31 depicts an exemplary steroid capsule 407 that may be placedwithin the steroid cavity 510 in the barrel section 506 of the tipelectrode 405. The steroid capsule 407 may be formed as a cylindricalplug sized to fit snugly within the steroid cavity 510. The steroidcapsule 407 may be any of a number of steroids or medicaments preparedin a binder for timed release after implantation of the lead 400 inorder to promote healing of any trauma caused by placement of the lead400 or to deliver a desirable drug for efficacy within the heart. Asnoted above, the steroid capsule 407 may be adhered within the barrelsection 506 with a biocompatible adhesive to ensure that the steroidcapsule 407 does not dislodge even after eluting.

FIGS. 32A and 32B depict an exemplary embodiment of a tip sleeve 409used to crimp the tip electrode 405 to the inner conductor coil 420. Thetip sleeve 409 is formed as a cylindrical sleeve 540 defining a tipsleeve bore 544 of a constant diameter therethrough. The diameter of thetip sleeve bore 544 is selected to be slightly smaller than the outerdiameter of the proximal shaft section 502 of the tip electrode 405 plustwo times the thickness of the wall of the inner conductor coil 420 inorder to provide a crimped connection with the proximal shaft section502 by sandwiching the inner conductor coil 420 therebetween. One ormore semicircular cutouts 542 may be formed in the cylindrical sleeve540 at the distal end thereof. The cutouts 542 may be provided to allowfor visual inspection of the crimp connection between the tip sleeve 409and the proximal shaft section 502 of the tip electrode 405 duringassembly.

The ring electrode 403 is depicted in greater detail in FIGS. 33A and33B. The ring electrode 403 is generally tubular in shape with variouscylindrical sections of varying diameter. A smooth, cylindrical proximalsleeve 550 forms the proximal end of the ring electrode 403 and is sizedin length and diameter to fit within the distal end of the outerconnecter coil 434 and may be laser welded thereto or otherwise securelymechanically attached to form a permanent mechanical and electricalconnection. An adhesive channel 552 is formed distally adjacent theproximal sleeve 550 and is defined by a proximal curb 551 and a distalcurb 553. The proximal curb 551 and the distal curb 553 may be of thesame diameter, which may be slightly larger in diameter than theproximal sleeve 550. The adhesive channel 552 may be substantially thesame diameter as the proximal sleeve 550. The proximal curb 551 mayseparate the proximal sleeve from the adhesive channel 552. Thediameters of the proximal and distal curbs 551, 553 are selected to besubstantially the same as the inner diameter of the outer sheath 452 andthe surfaces of the proximal and distal curbs 551, 553 are smooth inorder to provide a close compression fit with the outer sheath 452. Theadhesive channel 552 may define one or more adhesive apertures 554 (twoare shown in the exemplary embodiment) in order to introduce abiocompatible adhesive into the channel 552 to bond the ring electrode403 to the outer sheath 452.

The ring electrode 403 may transition from the adhesive channel 552 viaa proximal shoulder 555 adjacent the distal curb 553 to an exposedsection 556 of a greater outer diameter. The exposed section 556 may besmooth and cylindrical in shape and is not covered or insulated from thepatient's blood or tissue. The exposed section 556 may be made of aprecious metal, e.g., PT/Ir or Pt, or another electrically conductive,biocompatible material. The distal end of the exposed section 556transitions at a distal shoulder 557 to a connection section 560 thatmay be of a smaller outer diameter than the exposed section 556. Theconnection section 560 may be formed with a series of flat ribs 558separated from each other by a series of flat channels 559. The flatribs 558 may be selected to be of a diameter to increase the bondingsurface of the sleeve bore 528 of the passive tip sheath 408 forincreased bonding strength and to and create a tight connectiontherebetween. The flat channels 559 provide areas for a biocompatibleadhesive to be introduced and flow to thereby permanently adhere thesleeve bore 528 of the passive tip sheath 408 to the connection section560 at the distal end of the ring electrode 403.

The ring electrode 403 may also define a lumen of two different boresizes. A distal bore 562 is sized to be of a slightly larger diameterthan the insulating tubing 424 surrounding the inner conductor coil 420to provide clearance for its passage therethrough. A proximal bore 564is sized to be substantially the same diameter as the outer diameter ofthe insulating tubing 424 surrounding the inner conductor coil 420. Theinsulating tubing 424 and inner conductor coil 420 are thereby able topass through the proximal bore 564 during assembly. However, theadhesive in the adhesive channel 552 may pass through the adhesiveapertures 554 to contact the insulating tubing 424 and thereby adherethe insulating tubing 424 to the ring electrode 403 to act as a strainrelief on possible axial pull on the insulating tubing 424 that mightact to pull the insulating tubing 424 off of the tip sleeve 409 uponwhich the distal end of the insulating tubing 424 expands and terminatesas further described below. An interior shoulder 566 provides thetransition between the smaller diameter proximal bore 564 to the largerdiameter distal bore 562.

An exemplary alternate embodiment of a ring electrode 603 for use inconjunction with the passive tip sheath 608 of FIGS. 30C and 30D isdepicted in greater detail in FIGS. 34A and 34B. The ring electrode 603is generally tubular in shape with various cylindrical sections ofvarying diameter. A smooth, cylindrical proximal sleeve 650 forms theproximal end of the ring electrode 603 and is sized in length anddiameter to fit within the distal end of the outer connecter coil 434and may be laser welded thereto or otherwise securely mechanicallyattached to form a permanent mechanical and electrical connection.Several adhesive channels 652 are formed distally adjacent the proximalsleeve 650 and are defined by a proximal curb 651, a medial curb 659,and a distal curb 653. The proximal, medial, and distal curbs 651, 659,653 may be of the same diameter, which may be slightly larger indiameter than the proximal sleeve 650. The adhesive channels 652 may besubstantially the same diameter as the proximal sleeve 650. The proximalcurb 651 may separate the proximal sleeve from the first of the adhesivechannels 652. The diameters of the proximal, medial, and distal curbs651, 659, 653 are selected to be substantially the same as the innerdiameter of the outer sheath 452 and the surfaces of the proximal,medial, and distal curbs 651, 659, 653 are smooth in order to provide aclose compression fit with the outer sheath 452. One or more adhesiveapertures 654 (two are shown in the exemplary embodiment) may be definedin the area of the proximal, medial, and distal curbs 651, 659, 653 andthe adhesive channels 652 in order to introduce a biocompatible adhesiveinto the channels 652 to bond the ring electrode 603 to the outer sheath452.

The ring electrode 603 may transition to an exposed section 656 of agreater outer diameter from a proximal shoulder 655 adjacent the distalcurb 653. The exposed section 656 may be smooth and cylindrical in shapeand is not covered or insulated from the patient's blood or tissue. Theexposed section 656 may be made of a precious metal, e.g., PT/Ir or Pt,or another electrically conductive, biocompatible material. The distalend of the exposed section 656 may terminate at a distal rim 657 thatdefines a distal entrance to a lumen of the ring electrode 603. Thelumen may be formed with a proximal bore 664 of a smaller diameter thana distal bore 662. An interior shoulder 666 provides the transitionbetween the smaller diameter proximal bore 664 to the larger diameterdistal bore 662.

The distal bore 662 may be sized to be of an inner diameter slightlylarger than the protruding wall section 618 of the passive tip sheath608 to create a clearance fit with the passive tip sheath 608, which isof a larger diameter than the insulating tubing 424 surrounding theinner conductor coil 420 to provide clearance for its passagetherethrough. The recessed wall sections 616 of the passive tip sheath608 provide adhesive wells for receiving biocompatible adhesive topermanently connect the passive tip sheath 608 within the distal bore662 of the ring electrode 603.

The proximal bore 664 may be sized to be substantially the same diameteras the outer diameter of the insulating tubing 424 surrounding the innerconductor coil 420. The insulating tubing 424 and inner conductor coil420 are thereby able to pass through the proximal bore 664 duringassembly. However, the adhesive in the adhesive channels 652 may passthrough the adhesive apertures 654 to contact the insulating tubing 424and thereby adhere the insulating tubing 424 to the ring electrode 603to act as a strain relief on possible axial pull on the insulatingtubing 424 that might act to pull the insulating tubing 424 off of thetip sleeve 409 upon which the distal end of the insulating tubing 424expands and terminates as further described below.

With reference to FIG. 35, an alternative proximal end of the lead ofFIG. 24 is provided with a snap-fit connection between the passiveconnector insulator 1116 and the ring connector 1130. The passiveconnector insulator 1116 and the ring connector 1130 are designed tosnap together to axially secure the parts together. The snap engagementmay improve the mechanical strength of the connection joint between thecomponents. Additionally or alternatively, the snap engagement mayeliminate the use of medical adhesive or other bio-compatible glue forconnecting the passive connector insulator 1116 and the ring connector1130. Optionally, in some implementations, medical adhesive may be usedto further enhance the joint strength between the passive connectorinsulator 1116 and the ring connector 1130. In some embodiments, thesnap-fit connection features of the passive connector insulator 1116 andthe ring connector 1130 may be the same as those described above inrelation to FIGS. 21, 22A, 22B, 22C, 23A, and 23B (i.e., the tabs 705,905, 1105 may be provided on a passive connector insulator 416 of thetype shown in FIGS. 26A and 26B to form different embodiments of thepassive connector insulator 1116 and the ring connector 1130 may besimilar to or the same as the ring connector 730 in FIGS. 23A and 23B).Thus, the description of these interlock features will not be repeatedhere.

With reference to FIGS. 36A, 36B, and 36C, an alternative passiveconnector insulator 1216 is provided. The passive connector insulator1216 generally has the same features as the connector insulator 416depicted in FIGS. 26A and 26B except the cylindrical outer surface 1227of the inner shoulder 1290 is extended distally along the distalextension 1286 to accommodate a snap-fit connection feature. Inparticular, the connector insulator 1216 includes four tabs 1205 evenlyspaced about the periphery of the outer surface 1227. The tabs 1205 arepositioned about a distal portion of the outer surface 1227, therebydefining an annular recess 1207 located proximally of the tabs 1205. Thetabs 1205 each include a chamfered distal surface 1209, a substantiallysquare proximal shoulder 1213, and a curved surface 1211 locatedintermediate the chamfered surface 1209 and the square shoulder 1213.The curved surfaces 1211 of the tabs 1205 follow the curve of a cylinderaxially aligned with a center longitudinal axis of the passive connectorinsulator 1216. The interface between the chamfered surface 1209 and thecurved surface 1211 may be arcuate, curved, or rounded. The annularrecess 1207 is defined by the outer surface 1227, which serves as a basewall for the recess 1207. The base wall or outer surface 1227 of therecess 1207 is positioned between the square proximal shoulder 1213 andan opposing, radially-extending step surface 1232. The outer diameter ofthe tabs 1205 is greater than the inner diameter of annular recess 1207and may be less than the diameter of the outer surface 1229 of thecentral body 1282.

With reference to FIGS. 36D through 36F, another alternative connectorinsulator is provided. The insulator 1316 generally has the samefeatures as the connector insulator 1216 depicted in FIGS. 36A through36C except the tabs 1105 may be modified to reduce the cost andcomplexity of manufacturing the snap lock feature associated with thepassive connector insulator 1116. The connector insulator 1316 includesa plurality of tabs 1305 unevenly distributed about the periphery of theouter surface 1327. The tabs 1305 are symmetric with respect to thecross-sectional plane defining the cross section depicted in FIG. 36Eand include two upper tabs 1305A, 1305B and two lower tabs 1305C, 1305D.Each of the tabs 1305 includes a side surface 1353 that extends at anoblique angle from the outer surface 1327 of the recess 1307. The angledconfiguration of the side surfaces 1353 may reduce the cost andcomplexity of manufacturing the tabs 1305 without sacrificing mechanicalstrength of the snap-fit joint between the connector insulator 1316 andthe ring connector 1130, as previously discussed in connection with theconnector insulator 916. Although each tab 1305 includes only oneoblique side surface 1353 in FIGS. 36D through 36F, the tabs 1305 mayinclude any number of oblique side surfaces 1353. In one implementation,both side surfaces of each tab 1305 extend at oblique angles from theouter surface 1327 of the recess 1307. The oblique angle may betangential to the outer surface 1327. Alternatively, the side surfaces1353 may extend approximately perpendicular to the outer surface 1327.

Similar to the active connector insulator, the locking feature of thepassive connector insulator may include any number of tabs. Generally,at least one tab may extend continuously or discontinuously around theperiphery of the passive connector insulator. The at least one tab mayextend around a minority, one-half, or a majority of the circumferenceof the outer surface of the connector insulator. The at least one tabmay have a suitable cross-sectional shape to provide a suitableinterlock insertion and retention force. The at least one tab mayinclude a substantially square proximal shoulder to increase themechanical strength of the mechanical snap-fit joint between theconnector insulator and the ring connector. At least one side surface ofthe at least one tab may extend at an oblique angle, includingtangential, from a circumferential surface of the connector insulator toreduce the cost and/or complexity of manufacturing the locking featureof the connector insulator. Additionally or alternatively, at least oneside surface of the at least one tab may extend perpendicular relativeto an outer surface of the passive connector insulator.

One of the advantages of implementations of the present invention isthat most of the parts and components of the proximal end of the activeand passive leads can be shared, which significantly reduces the cost oftooling, manufacturing, and assembling. For example, the conductiveconnector pin 112, 412, the inner conductor or coil 120, 420, theinsulator tubing 124, 424, the pin sleeve 122, 422, the ring connector130, 430, and the outer conductor or coil 134, 434 of the proximal end102, 402 of the active and passive leads 100, 400, respectively, are thesame. The proximal seals 114, 414 and the connector insulators 116, 416of the proximal end 102, 402 of the active and passive leads 102, 402,respectively, differ slightly from one another. Accordingly, only twocomponents or parts of the proximal end 102, 402 of the active andpassive leads 100, 400, respectively, may be switched to transition froman active to a passive lead.

All directional references (e.g., proximal, distal, upper, lower,upward, downward, left, right, lateral, longitudinal, front, back, top,bottom, above, below, vertical, horizontal, radial, axial, clockwise,and counterclockwise) are only used for identification purposes to aidthe reader's understanding of the present invention, and do not createlimitations, particularly as to the position, orientation, or use of theinvention. Connection references (e.g., attached, coupled, connected,and joined) are to be construed broadly and may include intermediatemembers between a collection of elements and relative movement betweenelements unless otherwise indicated. As such, connection references donot necessarily infer that two elements are directly connected and infixed relation to each other. The exemplary drawings are for purposes ofillustration only and the dimensions, positions, order and relativesizes reflected in the drawings attached hereto may vary.

The above specification, examples and data provide a completedescription of the structure and use of exemplary embodiments of theinvention as defined in the claims. Although various embodiments of theclaimed invention have been described above with a certain degree ofparticularity, or with reference to one or more individual embodiments,those skilled in the art could make numerous alterations to thedisclosed embodiments without departing from the spirit or scope of theclaimed invention. Other embodiments are therefore contemplated. Many ofthe implementations described herein are not required and the order ofsteps or operation may be a matter of choice, dependent on theperformance requirements of the particular implementation. Accordingly,the operations making up the embodiments of the technology describedherein may be referred to variously as methods, operations, or steps. Itshould be understood that operations may be performed in any order,unless explicitly claimed otherwise or a specific order is inherentlynecessitated by the claim language. It is intended that all mattercontained in the above description and shown in the accompanyingdrawings shall be interpreted as illustrative only of particularembodiments and not limiting. Changes in detail or structure may be madewithout departing from the basic elements of the invention as defined inthe following claims.

1. A bipolar cardiac lead comprising: a connector pin having a proximalend and a distal end, the proximal end configured to engage anelectrical stimulation device; a connector insulator coupled to thedistal end of the connector pin; and a ring connector coupled to theconnector insulator with a snap-fit connection, wherein the connectorinsulator provides electrical insulation between the connector pin andthe ring connector.
 2. The bipolar cardiac lead of claim 1, wherein: thering connector includes an annular groove, and the connector insulatorincludes at least one tab configured to seat within the annular groove.3. The bipolar cardiac lead of claim 2, wherein the ring connectorfurther includes a radially inturned lip located proximally of theannular groove, the radially inturned lip includes a substantially flatface, a retaining shoulder located distally of the substantially flatface, and an inner cylindrical surface located intermediate thesubstantially flat face and the retaining shoulder.
 4. (canceled)
 5. Thebipolar cardiac lead of claim 3, wherein the radially inturned lipfurther includes a chamfered interface between the inner cylindricalsurface and the substantially flat face, and wherein the retainingshoulder is oriented substantially perpendicular to the innercylindrical surface.
 6. (canceled)
 7. The bipolar cardiac lead of claim2, wherein the at least one tab comprises a plurality of tabs extendingoutwardly from a periphery of the connector insulator, and wherein theplurality of tabs are distributed on the periphery of the connectorinsulator. 8-12. (canceled)
 13. The bipolar cardiac lead of claim 2,wherein the at least one tab includes a chamfered distal surface, asubstantially square proximal shoulder, and a substantially curvedsurface located intermediate the distal surface and the proximalshoulder.
 14. The bipolar cardiac lead of claim 2, wherein the at leastone tab includes a side surface that extends at an oblique angle from acircumferential surface of the connector insulator. 15-16. (canceled)17. The bipolar cardiac lead of claim 1, further comprising an innerconductor coupled to the distal end of the connector pin and extendingaxially through the lead.
 18. The bipolar cardiac lead of claim 17,wherein the connector insulator includes a proximal extension and adistal extension, and wherein the distal extension is disposed aroundthe inner conductor.
 19. The bipolar cardiac lead of claim 17, furthercomprising a proximal seal disposed around the proximal extension of theconnector insulator, the proximal seal configured to sealingly engagethe electrical stimulation device.
 20. The bipolar cardiac lead of claim17, further comprising insulating tubing coupled to the distal extensionof the connector insulator, the insulating tubing disposed around theinner conductor and around the distal extension of the connectorinsulator, wherein the ring connector is disposed around the insulatingtubing.
 21. (canceled)
 22. A connector insulator for use with a cardiaclead to provide electrical insulation between a connector pin and a ringconnector, the connector insulator comprising a body; a proximalextension extending from the body in a proximal direction andconnectable to the connector pin; and a distal extension extending fromthe body in a distal direction and connectable to the ring connector,the distal extension including at least one tab extending radiallyoutward from an outer surface of the distal extension, the at least onetab spaced from the body in a distal direction to define an annularrecess between the at least one tab and the body.
 23. The connectorinsulator of claim 22, wherein the at least one tab includes a chamfereddistal surface, a substantially square proximal shoulder, and asubstantially curved surface located intermediate the distal surface andthe proximal shoulder. 24-26. (canceled)
 27. The connector insulator ofclaim 22, wherein the at least one tab comprises a plurality of tabssymmetrically spaced about the outer surface of the distal extension.28-31. (canceled)
 32. The connector insulator of claim 22, wherein thedistal extension extends from the body in the distal direction from aset of cascading shoulders, and wherein the at least one tab extendsradially outward from a surface of the set of cascading shoulders.
 33. Aring connector for use with a cardiac lead to electrically communicatewith an electrical stimulation device and connectable to a connectorinsulator, the ring connector comprising: a band portion including anexposed outer surface configured to electrically communicate with theelectrical stimulation device and an inner wall defining an inner cavityconfigured to receive a portion of the connector insulator, the innerwall including an annular groove spaced distally from a proximal face ofthe ring connector to define a radially inturned lip intermediate theproximal face and the annular groove; and a crimp portion arrangeddistally to the band portion.
 34. The ring connector of claim 33,wherein the radially inturned lip includes a retaining shoulder spaceddistally from the proximal face and a cylindrical surface intermediatethe proximal face and the retaining shoulder.
 35. The ring connector ofclaim 34, wherein the radially inturned lip further includes a chamferedinterface between the cylindrical surface and the proximal face, whereinthe retaining shoulder is oriented substantially perpendicular to thecylindrical surface.
 36. (canceled)
 37. The ring connector of claim 34,wherein the inner wall further includes a limit shoulder spaced distallyfrom the retaining shoulder, and wherein the limit shoulder is angledrelative to the retaining shoulder.
 38. (canceled)
 39. The ringconnector of claim 33, further comprising a slot portion arrangedintermediate the band portion and the crimp portion.